System and method for monitoring a workstation remotely

Abstract

The invention relates to a system and a method that allow a workstation (A.1, A.2) to be monitored remotely. A monitoring unit for the workstation comprises a camera (2.1, 2.2, 2.3), a gas measuring device (1.1, 1.2, 1.3, 1.4) and a workstation computer (3.1, 3.2). The system furthermore comprises a communication unit (10) and a control centre having a central output computer and an output unit. Signals from the camera (2.1, 2.2, 2.3) and the gas measuring device (1.1, 1.2, 1.3, 1.4) are transferred to the workstation computer (3.1, 3.2) by cable or wirelessly and from there on to the communication unit (10) by cable or wirelessly. The signals are transferred from the communication unit (10) to the central output computer wirelessly. The central output computer causes the received signals to be output on the output unit in a form that is apparent to a human being. The data connection between the communication unit (10) and the central output computer is preferably routed via a public mobile radio network.

Description

5 The invention relates to a monitoring system and a monitoring process for remotely monitoring at least one workplace, namely during a period in which at least one human is at least temporarily performing work at the workplace. Harmful gases may escape and other events hazardous to humans may occur at the workplace. 10 The object of the invention is to provide a monitoring system and a monitoring method which make it possible to monitor at least one workplace remotely. At least one human performs work at this workplace. Pollutants that are dangerous to a human may be emitted at the workplace. The monitoring system and the monitoring procedure should be able to be set up relatively quickly. 15 The object is achieved by a monitoring system with the features of claim 1 and by a monitoring process with the features of claim 24. Advantageous embodiments of the monitoring system according to the invention are, as far as useful, also advantageous embodiments of the monitoring process according to the invention and vice versa. 20 The monitoring system according to the invention and the monitoring process according to the invention enable at least one workplace to be monitored remotely. Preferably, the monitoring system according to the invention and the monitoring process according to the invention allow at least two workplaces to be monitored remotely at the same time. 25 The monitoring system according to the invention comprises for the or each monitored workplace at least one respective monitoring unit, optionally at least two monitoring units for at least one monitored workplace. The or each monitoring unit comprises respectively - at least one camera, optionally at least two cameras, 2023345418   13 Jul 2026 - at least one gas measuring device, optionally at least two gas measuring devices, and - a signal-processing workplace computer. The or each camera of a monitoring unit is capable of generating an image 5 signal of the monitored workplace. The image signal shows completely or at least partially the workplace and preferably comprises a sequence of images, in particular a video sequence, of the workplace. The or each camera is preferably configured to generate the image signal during the entire time period in which the workplace is monitored. It is possible that the monitoring system comprises 10 at least two cameras, each of these two cameras generating in one application a respective image signal from the same workplace and generating in one application image signals from two different workplaces. A camera, a gas measuring device, and the workplace computer of a monitoring unit may each be located in the workplace or outside the workplace. It is possible that a 15 camera and / or a gas measuring device are arranged in the workplace and another camera and / or another gas measuring device are arranged outside the same workplace and the latter generates signals from the workplace from the outside. The or each gas measuring device of a monitoring unit is capable of measuring 20 an indicator for the respective concentration of at least one target gas that occurs or can occur in or at the monitored workplace. Optionally, the or at least one gas measuring device is capable of simultaneously measuring an indicator for the respective concentration of at least two target gases. The or one target gas is, in particular, a combustible or toxic gas or other gas that is harmful or 25 dangerous to a human. It is also possible that the gas measuring device measures whether the oxygen concentration at the workplace is sufficiently high. In a first alternative, the or each gas measurement device at a workplace is capable of comparing a measured target gas concentration to a specified concentration threshold. In a second alternative, a target gas concentration 30 measured by a gas measuring device at a workplace is transmitted to the workplace computer of the monitoring unit for that workplace, and the workplace computer compares the target gas concentration with the concentration 2023345418   13 Jul 2026 threshold. If the measured target gas concentration is above the concentration threshold or generally outside a specified range of values, the gas measuring device (first alternative) or the workplace computer (second alternative) is capable of automatically generating an alarm and triggering transmission of the 5 alarm to a spatially remote receiver. It is also possible that the alarm is triggered when the target gas concentration is below the concentration threshold. An example of this is the oxygen concentration at the workplace, which must not fall below a predefined threshold. It is possible, but thanks to the invention not required, that a human compares 10 the measured target gas concentration with the concentration threshold and triggers an alarm. Further, it is possible, but thanks to the invention not required, for the central output computer or an optional central computer to receive a signal containing the measured target gas concentration from the monitoring unit and to apply a decision rule to that signal to generate an alarm. This 15 potential embodiment would require a measured target gas concentration to be transmitted from the monitoring unit to the first control center. The invention allows a measured target gas concentration to be transmitted to the first control center, but eliminates the need for such data transmission. Thus, the invention saves data traffic, in particular data traffic from the first control center to a 20 monitoring unit. It is also possible that both the alarm and the message with the measured target gas concentration are optionally transmitted to the first control center with the type of detected target gas. Because the monitoring unit generates the alarm, it is possible to transmit the alarm to the first control center with a higher 25 priority than the target gas concentration. This embodiment is particularly advantageous if a public mobile radio network is used to transmit messages from the communication unit to the first control center. The message with the target gas concentration makes it easier for an operator at the first control center to assess the situation at the workplace at which the alarm was 30 triggered. 2023345418   13 Jul 2026 If the central output computer or an optional central computer were to apply a decision rule to the measured target gas concentration, it would be necessary to store and keep updated the decision rule in the central output computer or the optional central computer. In particular, it would generally be necessary to keep 5 on hand an upper limit for a harmful target gas and / or a lower limit for the oxygen concentration, for example. The danger would arise that the decision rule would not be up to date or that no decision rule would be available for a gas measuring device used in the control center. The invention thus reduces the risk that a target gas is not detected or that a false alarm is generated. 10 In one embodiment, at least one gas measuring device itself or the monitoring unit for the monitored workplace issues (outputs) an alarm. Thus, in this embodiment, the alarm is issued both in or at the workplace and at the first control center. The output at the workplace and the output at the first control center are based on the same target gas measurement and the same 15 concentration threshold. The invention eliminates the need to transmit a signal containing the target gas concentration to the central output computer or optional central computer and then, conversely, transmit an alarm back to the workplace. This generates additional data traffic and can result in a time delay. It is possible for a worker at the workplace to carry the or a gas measuring 20 device while performing the work at the workplace. Preferably, however, the or at least one gas measuring device is stationary at a workplace, at least as long as the workplace is monitored. This enables the gas measuring device to measure a target gas concentration in an area of the workplace even if no person with a gas measuring device is currently present in this area. In 25 particular, it is possible to warn a person before entering this area. Furthermore, in many cases, fewer gas measuring devices are required in this embodiment than there are workers at the workplace. It is possible that at least one gas measuring device is arranged stationary at a workplace and at least one further gas measuring device is carried by a worker at this workplace. 30 Preferably, the or each gas measuring device is configured to measure the target gas concentration and compare it to the concentration threshold 2023345418   13 Jul 2026 throughout the time period in which the workplace is being monitored. It is possible that the monitoring system comprises at least two gas measuring devices, wherein in one application the two gas measuring devices measure target gas concentrations at the same workplace, in particular of two different 5 target gases, and in another application target gas concentrations at two different workplaces. During an operation, the or each camera and the or each gas measuring device of a monitoring unit are permanently or at least temporarily connected or connectable to the workplace computer of this monitoring unit, namely by cable 10 and / or wirelessly, in particular by radio waves. Preferably, the connection by cable can be disconnected again. Thanks to this wired or wireless data connection, the or each camera and the or each gas measuring device are able to transmit a respective signal to the workplace computer. In particular, the or each gas measuring device is able to transmit an alarm and optionally a 15 measured target gas concentration to the workplace computer. It is possible that a data connection to the workplace computer can be established either by cable or wirelessly. If the camera or the gas measuring device are connected to the workplace computer by cable, the cable is used for transmitting the signal, otherwise the signal is transmitted wirelessly, in 20 particular by radio waves. Optionally, the workplace computer is able to trigger a data transmission in the opposite direction and thereby transmit a message to at least one connected device of the monitoring unit. The monitoring system according to the invention further comprises a communication unit (router) and a first control center. The first control center is 25 physically remote from the communication unit and from the or each monitoring unit and is located outside the or each monitored workplace. In one embodiment, the communication unit is located outside the or each workplace and, in another embodiment, is located at or in the or each monitored workplace. The embodiment with the communication unit located outside the 30 workplace in many cases eliminates the need for the communication unit to meet a high requirement for explosion protection and / or resistance to harmful 2023345418   13 Jul 2026 gases. The feature with a separate communication unit thus makes it easier to comply with safety requirements. A data connection is established or can be established at least temporarily between the or each workplace computer and the communication unit. It is 5 possible that at least two workplace computers are connected to the same communication unit. This data connection uses a cable and / or wireless data transmission, in particular by radio waves. Preferably, a connection established by cable can be disconnected again. In one embodiment, this data connection is selectively established via a cable or wirelessly via radio waves. If a cable 10 connection is established, it is used for the data transmission, otherwise a data transmission via radio waves. The or each workplace computer is capable of transmitting signals from the or each connected camera, from the or each connected gas measuring device, and optionally from the or each further connected device to the communication 15 unit via this data connection. In particular, the workplace computer is capable of transmitting an alarm from a connected gas measuring device to the communication unit. Preferably, conversely, the workplace computer is capable of transmitting a message to at least one connected device of the monitoring unit. This message concerns, for example, the setting of a sensor at the 20 workplace. The first control center comprises a central output computer. A data connection is established or can at least temporarily be established between the communication unit and the central output computer. This data connection is or comprises a wireless data connection, in particular a data connection via radio 25 waves. In one embodiment, this data connection is established by using a public mobile radio network. Via this data connection, signals can be transmitted from the or each workplace computer via the communication unit to the central output computer. Preferably, a message can conversely be transmitted from the central output computer via the communication unit to the 30 or a workplace computer. 2023345418   13 Jul 2026 Both the or each workplace computer and the communication unit are capable of transmitting data, but over different distances. The workplace computer of the monitoring unit for a workplace receives data from the sensors in or at that workplace, in particular from the or each gas measuring device and the or each 5 camera, and forwards the data received from the sensors to the communication unit. Optionally, the or each workplace computer receives a message from the communication unit and forwards it to at least one connected sensor. In many cases, the workplace computer can be connected to at least one sensor using a cable, otherwise or additionally using a wireless data connection on a local area 10 network. The data connection between the workplace computer and the communication unit also only needs to bridge a relatively small distance and can be implemented with a cable and / or in a local network. The communication unit, on the other hand, receives data from the or each connected workplace computer and forwards it to the central output computer 15 over at least part of the transmission distance wirelessly, i.e., in a wide area network. Preferably, the distance between the communication unit and the central output computer is at least twice as great, and more preferably at least ten times as great, as the distance between the communication unit and the or each workplace computer. 20 The first control center further comprises at least one output unit. Preferably, the or at least one output unit comprises at least one display screen. Optionally, an output unit comprises a voice output unit. The central output computer is adapted to control the or each output unit. The controlled output unit is adapted to output in at least one form perceptible by a human a signal transmitted from 25 the monitoring unit to the central output computer, in particular the image signal of a camera and any alarm of a gas measuring device, and optionally a voice signal. The output unit is capable of outputting the signal in particular visually and / or acoustically and / or haptically (by vibrations). Preferably, the image signal is output visually and the alarm at least acoustically and / or haptically, 30 the voice signal acoustically. 2023345418   13 Jul 2026 The controlled output unit outputs for each monitored workplace a respective representation. On the one hand, the representation for a workplace shows each alarm from the or each gas measuring device at this workplace, namely in at least one form perceptible by a human being, preferably visually perceptible. 5 On the other hand, at any time during the monitoring, the representation shows the respective image signal from the or at least one camera at that workplace. The preferred embodiment that the alarm is visually output eliminates the need to acoustically notify the operator at the control center of an alarm. Such an acoustic output can be overheard, especially if the operator is currently 10 exchanging voice messages with a worker at a workplace. It is also possible to output in the first control center an alarm both visually and acoustically. It is also possible for an alarm to be output visually in the first control center and acoustically in another control center. The invention reduces the risk that a worker performing work at a monitored 15 workplace is injured at that workplace without anyone else noticing. In particular, thanks to the gas measuring device, the monitoring unit is able to detect whether a target gas has leaked in or at the workplace at a concentration above the concentration threshold or is present for some other reason, and then generate an alarm. As an image signal generated by a camera at the monitored 20 workplace is transmitted to the first control center, an operator at the first control center is enabled to remotely visually monitor the workplace. In particular, the operator can determine how many and what persons are currently in or at the monitored workplace, whether a worker at the workplace has suffered an accident or a fainting spell, and also whether or not each worker is wearing the 25 respective prescribed protective equipment. It is possible, but thanks to the output of the image signal not necessary, for an image evaluation unit to automatically search for unwanted events in the image signal of a camera. Because the first control center is physically remote from the or each monitored workplace, noxious gases, contaminants, and other mechanical or chemical 30 pollutants, as well as noise, are not capable of having a harmful effect on an operator or on the equipment in the first control center. Spatial restrictions that often apply at a monitored workplace do not affect the first control center. 2023345418   13 Jul 2026 The invention can be combined with the use of a safety (backup) post, i.e., a person who monitors the workplace on site. However, the invention obviates the need to provide such a safety post at the workplace. Rather, an operator can monitor a workplace remotely, namely from the first control center, optionally 5 monitor at least two workplaces simultaneously. According to the invention, a signal from a sensor of a monitoring unit is not transmitted directly to the central output computer, but to the workplace computer, from there to the communication unit and from there to the central output computer. In the same way, a message is transmitted in the opposite 10 direction. In particular, this feature has the following advantages: The workplace computer can be located in or near the monitored workplace and, in one embodiment, can supply electrical power to at least one sensor at the workplace. In some cases, a sensor can be connected to the workplace computer by means of a cable. The workplace computer is able to process 15 signals locally and optionally perform further calculations. Thanks to the workplace computer, it is not necessary to transmit measured values from a sensor at the workplace to the central output computer, to have them evaluated by the central output computer, and optionally to transmit an evaluation result back to the workplace. The configuration with the workplace computer thus 20 saves data traffic compared to a configuration in which measured values are transmitted directly from the sensors at the workplace to the central output computer, and reduces the risk of a time delay in data transmission. The communication unit eliminates the need to provide a device in or at a monitored workplace that is capable of transmitting data to the first control 25 center, thereby bridging the distance between the workplace and the first control center. It is sufficient that the workplace computer is able to transmit the signals from the sensors to the communication unit. The communication unit can be installed in or at a monitored workplace or in the vicinity of a workplace. Because only a relatively short distance has to be bridged between the 30 workplace computer and the communication unit, in many cases a local data network can be set up and used. The communication unit forwards signals 2023345418   13 Jul 2026 received from at least one workplace computer and does not necessarily need to perform any further calculations. Thanks to the workplace computer, the communication unit also does not need to be directly connected to a sensor at the workplace. It is possible to connect the communication unit to several 5 workplace computers for different workplaces. According to the invention, the data connection between the communication unit and the central output computer is established by means of a data connection, wherein this data connection comprises or is configured as a wireless data connection. In many cases, this feature makes it easier to position the central 10 output computer in a desired position relative to the or a monitoring unit, even at a great distance from or even close to a monitored workplace. The positioning of the central output computer is not limited by the maximum possible length of a cable or by the availability of a stationary power supply network in the vicinity of the monitored workplace. 15 According to the invention, the central output computer is able to control the or each output unit, and the controlled output unit generates for the or each monitored workplace a respective representation. The representation for the workplace shows the image signal of the or at least one, preferably each camera of this workplace as well as each alarm of the or each gas measuring 20 device, namely in at least one form perceptible by a human being, in particular visually, acoustically and / or haptically. According to the invention, for each monitored workplace a respective representation is output. This representation shows the respective image signal of the or each camera at this workplace at any time during the monitoring. 25 Therefore, an operator in the control center can remotely monitor the workplace at any time. In many cases, this embodiment provides a higher level of security compared to an embodiment in which an image signal is only displayed when a sensor or the monitoring unit at the workplace has generated an alarm. The operator in the control center can in many cases detect a possibly dangerous 30 situation by evaluating the image signal, even if this dangerous situation has not or not yet led to an alarm. It is possible, but thanks to the invention not 2023345418   13 Jul 2026 necessary, that an image evaluation unit automatically evaluates the image signals from the cameras at the workplaces and decides whether a dangerous situation has occurred. Such an image evaluation unit may in some cases not be able to detect a dangerous situation. Furthermore, such an image evaluation 5 unit could produce many false alarms. In a preferred embodiment, the wireless data connection between the communication unit and the central output computer - or the wirelessly implemented part of the transmission link - is implemented using a public mobile radio network. This embodiment eliminates the need to lay a cable or set up a 10 directional radio link specifically for monitoring the workplace. Instead, an infrastructure that is usually already available, namely an existing public mobile radio network, is used for monitoring. Therefore, the use of a public mobile radio network saves time required to set up the system and process according to the invention for monitoring the workplace and to dismantle it later if required. In 15 addition, the public mobile radio network is often capable of bridging a large distance between the communication unit and the central output computer. Therefore, the first control center can ideally be set up at any place on earth where a connection to a public mobile radio network is available. In one embodiment, this public mobile radio network is implemented with the aid 20 of at least one central computer. This central computer can be located remotely from the first control center, ideally also at any location on earth with a connection to a mobile radio network. Thanks to the public mobile radio network, the central computer is permanently or at least temporarily in a data connection with the communication unit and permanently or at least temporarily 25 in a data connection with the central output computer. In one embodiment, on this central computer a monitoring system area is provided and used for the monitoring system according to the invention. In one implementation, this monitoring system area is provided and used permanently for the monitoring system according to the invention, and in another 30 implementation, it is provided and used only for a specific time period during which the work is performed and completed at the or each monitored 2023345418   13 Jul 2026 workplace. It is possible that the monitoring system is used in a first time period for monitoring at least a first workplace and in a subsequent second time period for monitoring at least a second workplace. It is also possible that a monitoring system area on a first central computer is used in the first time period and a 5 monitoring system area on a second central computer is used in the second time period, wherein the two central computers may be different from each other and spatially remote from each other. At least one program is installed on this monitoring system area, including at least one processing program, for example a web server implemented as 10 software. When executed on the central computer, this processing program generates a data set that can be represented in at least one form that can be perceived by a human being, in particular visually and / or acoustically. The processing program uses the received signals from the monitoring units to generate this data set. This data set is hereinafter referred to as "processing". 15 This processing is transmitted to the central output computer, for example in response to a request from the central output computer. Preferably, this processing is continuously updated and transmitted. The processing comprises a visually displayable or otherwise displayable processing of each alarm from the or each gas measuring device, and a visual representation of the respective 20 image signal from each camera. Optionally, the processing includes representations of other signals from at least one device that is set up at a monitored workplace and connected to the workplace computer. According to the embodiment just described, the central output computer generates the control for the output unit using the processing generated by the 25 central computer and using an output program installed on the central output computer, for example a web browser. The representation, that the controlled output unit outputs, shows the displayable processing generated by the processing program in at least one form that can be perceived by a human. Preferably, a unique Internet address is assigned to the monitoring system area 30 used on the central computer. With the aid of the unique Internet address, the output program can query data and thus also the processing from the 2023345418   13 Jul 2026 monitoring system area. It is also possible that the communication unit is assigned a unique Internet address and the output program can query data from the communication unit. These two embodiments can be combined. Functionally, the monitoring system area on the central computer with the or 5 each processing program thus belongs to the first control center, even if it is installed on the central computer and not on the first control center. If it is specified below what the central output computer and / or generally the first control center can be configured for and / or what steps they can execute, this includes the possibility that some of these embodiments and steps are realized 10 and / or executed by the or each program on the central computer. The embodiment that the processing program, which generates the processing, is installed on the central computer makes it possible to use a central output computer, which requires a smaller computing capacity and / or storage capacity than if the output computer itself would generate the representation for 15 the output unit in the first control center and would use for this directly the alarms and signals from the or each workplace computer. This in turn allows the central output computer to be configured as a relatively small and lightweight device, particularly as a portable computer, especially a laptop or tablet or smartphone. The central computer, on the other hand, can be relatively easily 20 equipped with the necessary computing capacity. It does not require an output unit capable of outputting a signal from a device at a monitored workplace and also not an input unit. Optionally, the monitoring system comprises at least one second control center in addition to the first control center. The second control center is spatially 25 remote from the communication unit and from the or each monitored workplace, just like the first control center. In addition, the second control center is spatially remote from the first control center. Just like the first control center, the second control center includes a central output computer and an output unit. The monitoring system area of the central computer is permanently or at least 30 temporarily in a data connection with the second central output computer, that is, with the central output computer of the second control center. The second 2023345418   13 Jul 2026 central output computer is able to control the output unit of the second control center and to cause the second output unit to output a representation. Preferably, a further output program is installed on the further central output computer. The representation on the further output unit is generated like the 5 representation on the output unit of the first control center using that processing which the processing program on the central computer has generated. The same processing is thus displayed twice, namely on different output units. This embodiment makes it possible to monitor the or each workplace selectively in the first control center or in the second control center. Each control center is 10 permanently or at least temporarily in a data connection with the same monitoring system area of the central computer and uses the same processing that the processing program of the central computer has generated. Both control centers therefore use the same processing and thus the same signals from the devices at the monitored workplaces, and they do so simultaneously 15 except for possibly different transmission times. It is not necessary that an alarm or other signal be transmitted from a workplace computer to the first control center and from the first control center on to the other control center. Rather, the two control centers are arranged in parallel. On the one hand, the configuration with at least two control centers creates 20 redundancy because the or each workplace is monitored simultaneously by two operators in two control centers. This reduces the risk of a dangerous situation being overlooked. On the other hand, this configuration increases safety. Indeed, it is possible that an operator in one center can no longer perform the task of monitoring of the or each workplace, for example, due to a technical 25 defect or a weakness, or that there is human error. In this case, the other center is still available for monitoring. The physical distance between the two control centers reduces the risk of both control centers failing simultaneously due to a technical effect or an external impact. In some cases, the use of two control centers makes it easier to monitor the or 30 each workplace around the clock without having an operator in one center working at night. For this application, the two control centers are placed in 2023345418   13 Jul 2026 different time zones. Each control center is used during a time period that falls within a specified temporal range of the day in that time zone, for example, between 06:00 in the morning and 06:00 in the evening. Of course, it is also possible to monitor the same workplaces from three control centers. 5 It is possible that the second control center is implemented with the aid of a portable computer, in particular a tablet or smartphone. An operator can carry this device with him / her and perform monitoring from any location, especially in the vicinity of a monitored workplace. It is possible that an operator in the first control center is regularly requested to 10 enter a user input. If no user input is registered in the first control center within a time period of a specified duration, the system automatically switches to the second control center, optionally after a request to an operator in the first control center to now make a user input. This embodiment further increases the reliability of remote monitoring. 15 The advantages of the first control center described above, as well as the advantageous embodiments of the first control center described below, can be applied equally to the or each second control center. According to the invention, at least one image signal from a camera in or at a workplace is transmitted to the central output computer via the workplace 20 computer for this workplace, the communication unit, and the wireless data connection. Preferably, this transmission is carried out via a public mobile radio network, optionally via a directional radio link instead. This transmission requires bandwidth. In a public mobile radio network used according to the preferred embodiment, other communication units typically also consume 25 bandwidth, often at the same time, so that the monitoring system according to the invention at least temporarily competes with other communication units for the currently available bandwidth. The transmission of an image signal usually requires more bandwidth than the transmission of an alarm or other signal from a workplace. Therefore, the situation may arise where the currently available 30 bandwidth is insufficient to transmit the or each image signal to the central output computer with the maximum possible image quality. 2023345418   13 Jul 2026 An embodiment that solves this problem is described below. According to the embodiment with the mobile radio network and the central computer, signals from various devices of the monitoring unit are transmitted to the central computer and from there further as part of the processing to the central output 5 computer. These signals include at least one image signal generated by the or a camera of the monitoring unit. As a rule, the transmission of the image signal requires a significantly larger bandwidth than the transmission of the other signals from the devices of the monitoring unit. This is because the other signals generally do not include image data or even video data. 10 According to the embodiment, the or at least one, preferably each camera of the monitoring system has at least one externally changeable and bandwidthrelevant parameter. It is possible that at least one camera has several bandwidth-relevant parameters. The current value of a bandwidth-relevant parameter influences the bandwidth required to transmit an image signal from 15 this camera to a spatially remote receiver. By controlling the camera from outside, the currently used value of a bandwidth-relevant parameter can be changed. This change can be carried out during operation. During operation, the camera is used to monitor a workplace, and the camera generates an image signal. The monitoring system is able to automatically control the or at least 20 one, preferably each camera, which has at least one externally changeable and bandwidth-relevant parameter. The objective of this control is that the respective value of at least one bandwidth-relevant parameter is changed. The change due to the control causes that the bandwidth is changed, which bandwidth is required for transmitting the image signal from this camera. In 25 particular, the required bandwidth is at least temporarily reduced. It is also possible to temporarily increase the bandwidth in order to obtain an image signal with a higher image quality. In one embodiment, an operator in the control center causes by a corresponding user input the value of the or at least one bandwidth-relevant 30 parameter of a previously selected camera to be changed, thereby reducing or even increasing the required bandwidth. Preferably, the operator selects at least one camera, and the monitoring system automatically changes the value of the 2023345418   13 Jul 2026 or each bandwidth-relevant parameter of the selected camera. Optionally, the operator also determines whether to improve the image quality of the image signal from the selected camera or, alternatively, to accept that the image quality will be degraded. For example, the operator selects one camera and 5 thus specifies that the image signal from this camera need only currently have a lower image quality than other image signals. In a preferred embodiment, however, a component of the monitoring system is able to automatically determine an indicator for the bandwidth which is currently available in the public mobile radio network or in a directional radio link used for 10 transmitting signals from the communication unit to the central output computer. In particular, the monitoring system component is able to automatically detect an indication of insufficient bandwidth. Typically, signals are transmitted in the form of data packets. In this case, the monitoring system component is preferably able to detect the event that data packets are lost ("packet loss", 15 "packet drop"). The loss of data packets is an indication of insufficient bandwidth. The monitoring system is able to automatically control at least one camera with the aim of changing the value of the or at least one bandwidthrelevant parameter. It is possible, but thanks to this configuration not necessary, that the camera itself automatically changes the bandwidth. 20 These two embodiments can be combined. In this combination, both the operator can select a camera and the monitoring system can automatically control at least one camera with the aim of changing, in particular reducing, the required bandwidth. According to the embodiment just described, the component of the monitoring 25 system is able to automatically determine an indicator for the bandwidth that is currently available in the public mobile radio network used or in a directional radio link used to transmit signals from the communication unit to the central output computer. Different forms of implementation are possible as to which component of the monitoring system is able to determine this indicator for the 30 bandwidth. 2023345418   13 Jul 2026 In one implementation, the central output computer is able to determine the available bandwidth automatically. In another implementation, the communication unit does this. In a preferred implementation, on the other hand, the or each workplace computer of a monitoring unit is able to automatically 5 determine the indicator of the currently available bandwidth. The determined bandwidth refers to the transmission path from the workplace computer via the communication unit to the central output computer or to an optional central computer. The determined bandwidth can be different for different workplace computers. 10 In particular, the embodiment that the workplace computer determines the indicator for the bandwidth has the following advantage: The transmission of an image signal from a camera to the central output computer requires the most bandwidth. The image signal from the camera is transmitted via a transmission path. This transmission path comprises a first part between the camera and the 15 workplace computer and a second part between the workplace computer and the central output computer. The first part can be realized by a cable and / or a local wireless network and usually provides sufficient bandwidth. Insufficient bandwidth usually only affects the second part of the transmission path, i.e. the transmission from the communication unit to the central output computer. The 20 workplace computer is usually better able to determine the bandwidth in this second part of the transmission path than the central output computer or an optional central computer. In addition, this embodiment eliminates the need to transmit a message to the workplace computer using the available bandwidth. Preferably, the workplace computer causes a different value to be assigned to 25 the bandwidth-relevant parameter of the connected camera. In one implementation, a data connection between the communication unit and the central output computer is established using a public mobile radio network, and this public mobile radio network is implemented using at least one central computer. In one embodiment, the monitoring system according to the invention 30 uses a monitoring system area of the central computer. On this central computer, the processing program described above may be installed and belong to the monitoring system area. It is possible that the central output 2023345418   13 Jul 2026 computer or the communication unit or also the or a workplace computer queries the available bandwidth from the central computer. The image quality with which image signals are displayed on an output unit in a control center generally depends essentially on the bandwidth currently 5 available in the public mobile radio network or in a directional radio link used. The bandwidth available in the data connection between the workplace computer and the communication unit or in the data connection between the camera and the workplace computer of a monitoring unit, on the other hand, generally has little influence on image quality. As a rule, there are no other 10 communication units competing for the bandwidth available for data transmission from the camera to the communication unit. Therefore, the workplace computer is usually able to detect insufficient bandwidth, even if the workplace computer is not directly connected to the public mobile radio network. Preferably, the workplace computer is able to control the or each camera 15 connected to it with the objective of changing the value of the bandwidthrelevant parameter and thereby reducing or also increasing the required bandwidth. Particularly preferably, the workplace computer is able to cause the respective parameter value of the or each connected camera to be changed, in response to the determination of the currently available bandwidth. The last 20 described implementation, in which the workplace computer itself determines the indicator for the currently available bandwidth, eliminates the need for a message concerning the available bandwidth to be transmitted to this workplace computer. Rather, each workplace computer reduces or even increases the respective required bandwidth as needed, independently of the or each other 25 workplace computer and also independently of the communication unit and the central output computer and the optional central computer. In many cases, this has the particular effect of rapidly reducing the required bandwidth. In many cases, it is ensured that - despite lower bandwidth - every image signal is still transmitted to the central output computer, albeit possibly with lower image 30 quality. This ensures that, even with lower bandwidth, the or each workplace is continuously monitored. 2023345418   13 Jul 2026 The embodiment that the workplace computer controls the or each camera with the objective of changing the value of the bandwidth-relevant parameter saves on the one hand the necessity that the central output computer directly controls the camera. Thus, data traffic is saved, and the risk of large latency is reduced. 5 In addition, this embodiment eliminates the need for the camera itself to have a control device capable of changing the parameter value depending on an available bandwidth. This makes it easier to implement the camera. In many cases, it is made easier for the camera to meet specified safety requirements, for example, for explosion protection. 10 According to the embodiment just described, a component of the monitoring system, in particular a workplace computer, is able to automatically change at least one value of a bandwidth-relevant parameter of a camera and thereby reduce or also increase the bandwidth required for transmitting an image signal from this camera to a spatially remote receiver. Preferably, the workplace 15 computer is able to control the camera and thereby change the parameter value. The implementation described below leads to the following result: The more people are currently at a workplace, the more bandwidth is available to transmit an image signal from a camera located in or at this workplace, and the higher is 20 the image quality of the image signal. This effect is advantageous for the following reason: The more people there are in or at the workplace, the greater is the risk, as a rule, that people will be injured there due to an accident or other event, or the greater is the risk that a person will not be wearing the prescribed protective equipment. Therefore, it is desirable that the more people there are, 25 the higher is the image quality with which images from that workplace are displayed on the output unit. If there is currently no person there, the image quality may be lower, and less bandwidth is required. Different implementations are possible to determine how many people are currently at a workplace. It is possible that the operator in the control center 30 counts how many people are shown in an image signal, this image signal originating from a camera at this workplace. It is also possible that an image 2023345418   13 Jul 2026 evaluation unit evaluates the or each image signal from the or a camera to determine the number of persons present. The implementation described below avoids the need for an operator or even an image evaluation unit to count the people. This implementation can be combined with counting by evaluating a 5 displayed image signal. According to this implementation, the monitoring unit includes at least one access control unit. Preferably, a person logs on to this access control unit when entering the workplace and logs off again when leaving the workplace. Each logon and logoff results in a signal of the access control unit. 10 With the help of signals of this access control unit, the monitoring system is able to determine how many people are currently in or at this workplace. In one implementation, the workplace computer for this workplace determines how many people are at the workplace. This implementation eliminates the need to transmit signals from the access control unit to the first control center. In 15 another implementation, the central output computer or an optional central computer determines the number of people. This implementation eliminates the need to equip the workplace computer with the necessary computing capacity. It is also possible for the access control unit itself to count how many people are currently in or at the monitored workplace. 20 In all implementations, the determined number of persons currently in or at the workplace and preferably an identifier for each person is output on the or an output unit of the control center in a form that can be perceived by a human being, in particular visually. In order to determine the number of people at the monitored workplace, in one 25 implementation the central output computer uses the signals from the access control unit, with these signals being transmitted to the central output computer via the workplace computer and the communication unit. In a preferred embodiment, the above-mentioned optional central computer for the public mobile radio network automatically counts how many people are currently in or 30 at the workplace and inserts the result of the count into the above-described processing. For counting, the central computer uses signals from the access 2023345418   13 Jul 2026 control unit. The workplace computer queries the central computer for the determined number of persons, in particular as part of the queried processing. In one implementation, the workplace computer uses signals from the access control unit to determine how many people are currently at the monitored 5 workplace, and optionally what people these are. In another implementation, the workplace computer merely detects the event that a person has logged in or logged out and transmits a corresponding message to the central output computer. Preferably, this message comprises a detected unique identifier of the person who has logged in or logged out. The central output computer or the 10 central computer or the workplace computer counts how many persons are currently in or at the monitored workplace according to the signals from the access control unit. An embodiment has already been described above in which the monitoring system is able to control the or at least one camera at a monitored workplace 15 with the objective of changing the value of a bandwidth-relevant parameter. Preferably, the workplace computer itself is able to control the camera. A suitable control of the camera reduces the data traffic between the first control center and the monitoring unit for the workplace. This embodiment can be combined with the embodiment of determining the number of persons currently 20 in or at the monitored workplace. In many cases, the combination results in less bandwidth being required to transmit an image signal from the workplace without significantly reducing the reliability of the monitoring. According to this combination, the monitoring system is able to control the camera depending on the determined number of persons. Preferably, the 25 workplace computer of the monitoring unit performs the control for the workplace. The control changes the value of the bandwidth-relevant parameter if needed. One objective of the control is that the lower the determined number of persons is, the lower is the required bandwidth. This is because, in many cases, the image signal may show less detail with a low number of people than 30 with a high number. On the other hand, the controlled camera continuously transmits an image signal during monitoring, i.e., even when the access control 2023345418   13 Jul 2026 unit has not detected a person. In particular, this takes into account the possibility that a person may be in or at the workplace without having been registered by the access control unit. Furthermore, in many cases it is possible to warn a person before entering the workplace, for example if a dangerously 5 high target gas concentration or a mechanical hazard occurs there, in particular a visually detectable one. Using a signal from the access control unit for a workplace, a component of the monitoring system, such as the workplace computer, may determine that no person is currently in or at the workplace. However, this result may be 10 erroneous, particularly if a person has entered the workplace without logging in to the access control unit, or if the access control unit erroneously fails to register a person's log-in, or if a signal from the access control unit is not transmitted to the workplace computer. Therefore, also in this case, an image signal is preferably transmitted from the workplace to the central output 15 computer, preferably with a relatively low image quality. According to the embodiment just described, at least one camera can be controlled with the objective of assigning a different value to a bandwidthrelevant parameter of the camera. As a result, the bandwidth required to transmit the image signal of this camera to the central output computer is 20 changed. As a rule, the more bandwidth is used to transmit the image signal, the greater is the image quality. In order to achieve the highest possible image quality, in a preferred embodiment the image quality is increased on a trial basis. This is done by assigning a correspondingly changed value to at least one bandwidth- 25 relevant parameter on a trial basis. The change is achieved by an external control while the workplace is being monitored, preferably by the workplace computer. It is checked automatically whether after the assignment the bandwidth is currently sufficient to transmit an image signal for a higher image quality or not. Preferably, this check checks whether data packets are lost. If the 30 bandwidth is not sufficient, the same or also another bandwidth-relevant parameter of the camera or another camera at the same workplace is assigned 2023345418   13 Jul 2026 a different value with the objective of reducing the required bandwidth again. In many cases, this configuration results in the available bandwidth being well utilized and an image signal with a high image quality being transmitted, even if the total available bandwidth varies over time. This step can be repeated on a 5 regular basis. As explained above, in one embodiment, a component of the monitoring system, preferably the or a workplace computer, is capable of controlling the or at least one camera, preferably each camera, with the objective of assigning a different value to at least one bandwidth-relevant parameter of the camera and 10 then using this parameter. The parameter value affects the bandwidth required to transmit the image signal from that camera to a spatially distant receiver. Typically, the greater the bandwidth used, the greater the image quality with which the image signal is visually displayed in the control center. A preferred implementation of a camera with several bandwidth-relevant parameters is 15 described below. According to this implementation, the or at least one camera comprises a photosensor and a signal-processing image processing unit and preferably its own control unit. The photosensor is capable of generating images depending on impinging electromagnetic waves, in particular light beams, and of storing 20 them at least temporarily in a data memory of the camera. Two bandwidthrelevant parameters concerning the photosensor are - the resolution (number of pixels) this is the number of pixels of an image that the photosensor generates, and - the frame rate ("frames per second"), that is the number of frames per time 25 unit with which the photosensor generates images. The camera can be controlled externally with the objective of changing the resolution and / or frame rate. The image processing unit generates the image signal, which signal is transmitted from this camera to the central output computer and output on the 30 output unit in a manner that can be perceived by a human. To generate the image signal, the image processing unit uses images from the photosensor and 2023345418   13 Jul 2026 applies an algorithm to these images. Another bandwidth-relevant parameter is a parameter of the algorithm that the image processing unit applies. Preferably, the algorithm causes the images of the photosensor to be compressed so that the image signal requires less bandwidth than if the images of the photosensor 5 were transmitted without processing with compression. The image processing unit parameter affects the algorithm that the image processing unit uses to process images of the photosensor to generate the image signal, and is therefore another bandwidth-relevant parameter. Preferably, the parameter influences the compression rate that the image processing unit achieves. By 10 controlling it from outside, a different value can be assigned to the parameter for the algorithm. It is possible that several bandwidth-relevant parameters influence this algorithm and that a respective different value can be assigned to each of these parameters independently of one another by an external control. In total, therefore, a camera in many cases has at least three bandwidth- 15 relevant parameters, i.e. at least three parameters whose values influence the bandwidth required to transmit an image signal from this camera to the central output computer. At least one of the bandwidth-relevant parameters mentioned can be changed by external control, preferably at least two parameters. Particularly preferably, 20 at least two or even all parameters can be changed independently of each other. A camera often has the bandwidth-relevant parameters just mentioned. It is also possible that only one of these parameters can be changed by external control and that each of the others remains constant during use. According to the invention, the controlled output unit outputs for each monitored 25 workplace one respective representation. During the monitoring, this representation for a workplace shows each alarm from the or each gas measuring device at this workplace as well as at each time during the monitoring the respective image signal of at least one camera, preferably each camera, at this workplace. 30 In one embodiment, the output unit comprises a screen. On this screen, for the or each monitored workplace a respective representation is output, which 2023345418   13 Jul 2026 representation functions as the or a representation within the meaning of the patent claims. Thus, if n workplaces are monitored simultaneously, n representations are simultaneously output on this screen. An operator in the control center can thus simultaneously monitor n workplaces while looking at 5 the screen. For outputting the representation, to each monitored workplace a respective area is assigned on the screen, i.e. for n monitored workplaces n different screen areas on the same screen, and the representation for the workplace is output in this assigned screen area. The representation which is output in the 10 screen area for a monitored workplace shows, on the one hand, the respective image signal from the or each camera at this workplace. On the other hand, the representation in the screen area comprises visually perceptible information as to whether or not the or at least one gas measuring device or the workplace computer at this workplace is currently generating an alarm. It is possible to 15 additionally output such an alarm acoustically or haptically (by vibrations). In one embodiment, the display for a monitored workplace additionally comprises an identification of this workplace. According to this embodiment, both the image signal and the information as to whether or not there is an alarm at the workplace are output visually in the 20 same screen area. It is possible but not necessary to additionally output a measured target gas concentration in this screen area. This feature of the embodiment leads to a particularly ergonomic display. An operator in the first control center can assign an alarm to an image signal or vice versa an image signal to an alarm quasi at a glance. The operator recognizes at a glance at 25 which workplaces an alarm concerning a harmful target gas concentration is currently generated, and at the same time sees at least one image signal from this workplace without having to let his or her attention wander back and forth between two different screens or screen areas. The operator does not need to evaluate a textual description of a workplace or detect an audible output of an 30 alarm to associate an alarm with an image signal or vice versa. In many cases, this embodiment allows multiple workplaces to be reliably monitored simultaneously in the same first control center. 2023345418   13 Jul 2026 In many cases it is not necessary to output by a separate information to which workplace an alarm refers. Furthermore, thanks to this configuration, the user does not need to switch between a visual and another display mode, in particular not between a visual display of an image signal and an acoustic 5 output of an alarm. This feature is particularly advantageous and leads to a particularly ergonomic monitoring if an operator in the control center monitors several workplaces simultaneously. It is possible that the output unit comprises at least one further screen. Preferably, more detailed information about a workplace is output on this further 10 screen if the or a gas measuring device or the workplace computer has generated an alarm at this workplace or when the operator has previously selected this workplace. In one implementation, the detailed information includes the or at least one, preferably each, measured target gas concentration at that workplace. 15 The monitoring system according to the invention can be used to permanently monitor at least one workplace remotely. According to another application, the monitoring system according to the invention is used to remotely monitor at least one workplace only during a specified time period. During this time period, at least one work task is performed and completed in or at the monitored 20 workplace. Preferably, a technician assembles the monitoring system or at least the monitoring unit until the beginning of this time period, enables monitoring of the workplace from the control center during this time period, and disassembles the monitoring system or at least the monitoring unit after completion of the work task. It is possible that the same monitoring system is subsequently used 25 to monitor at least one other workplace. The same control center at the same location, as well as the same monitoring unit, can be used to remotely monitor first a first workplace and then a second workplace. Because the monitoring system or at least one monitoring unit can be assembled and disassembled, devices of the monitoring system can be reused, especially devices of the or a 30 monitoring unit as well as the communication unit. 2023345418   13 Jul 2026 This application requires the monitoring unit to be transported to the vicinity of the workplace to be monitored, the workplace computer, the or each camera, the or each gas measuring device, and optionally at least one other device of the monitoring unit to be brought into a respective desired position relative to 5 the workplace to be monitored, and then the necessary data connections to be established. This is facilitated if the entire monitoring unit can be carried by a human and no vehicle or crane is required for transportation. Therefore, the devices of a monitoring unit preferably have a total mass (summed mass) of at most 20 kg, especially preferably at most 10 kg. This embodiment allows a 10 human to transport the devices to the workplace in a suitable container, for example in a backpack, and a technician to assemble the devices there. Preferably, the devices of the control center and the communication unit can also be transported by a single person. Particularly preferably, the total weight of all the devices of the control center is at most 50 kg, in particular at most 20 15 kg. Preferably, the weight of the communication unit is less than 5 kg, particularly preferably less than 2 kg. This embodiment makes it possible to set up the or a control center for an operation in sufficient proximity to the or at least one monitoring unit and to dismantle it again after an operation. "Sufficient proximity" means, in particular, that the public mobile radio network used or the 20 directional radio link used is sufficient for the transmission of signals to the central output computer. The control center devices can be used sequentially to monitor different workplaces. Preferably, the processing program described above and optionally other functions of the control center are not installed on the central output computer, but on the central computer for the public mobile 25 radio network described above. This embodiment makes it easier to transport the control center devices. Preferably, each device of the or each monitoring unit is configured as an intrinsically safe device. i.e. complies with requirements to explosion protection. In particular, suitable components of each device ensure that the current 30 intensity and the electrical voltage as well as the emission of thermal energy are limited at any time during operation and that no sparks escape. The device can therefore be used in a potentially explosive environment, in particular an 2023345418   13 Jul 2026 environment in which at least one flammable target gas can escape. In many cases, configuration of the monitoring unit exclusively with intrinsically safe devices allows the following procedure: The devices of a monitoring unit are transported individually to the workplace to be monitored, and the devices to 5 form the monitoring unit are assembled only at the workplace. Because the devices are intrinsically safe, this procedure is possible even if this workplace is a potentially explosive environment. In many cases, it is possible, but thanks to the intrinsically safe devices not necessary, to assemble the monitoring unit outside the workplace in a non-hazardous environment and then transport the 10 assembled monitoring unit as a whole to the workplace. It is often desired that a person in or at the or a monitored workplace and an operator in or at a control center can exchange voice messages. Therefore, in a preferred embodiment the or at least one monitoring unit comprises a voice input unit and a voice output unit, which preferably comprise a microphone and 15 a speaker and are located in or at the monitored workplace. The control center also comprises a voice input unit and a voice output unit, which preferably comprise a headset and a microphone. Thanks to the headset, the operator can listen to voice messages without being disturbed or distracted by noise in his or her environment. A person in or at the monitored workplace can enter a voice 20 message into the voice input unit at the workplace, which message is transmitted via the workplace computer, the communication unit, the wireless data connection, and the central output computer to the voice output unit in the control center, where it is output acoustically, preferably on the headset. Conversely, an operator at the central office can input a voice message into the 25 voice input unit at the central office, and this voice message is transmitted to the workplace via the central output computer, the wireless data connection, the communication unit, and the workplace computer, and is output acoustically there, preferably on the loudspeaker there. The use of a loudspeaker at the workplace eliminates the need for a worker to use a headset at the workplace. 30 However, it is also possible for the voice output unit at a workplace to additionally include a headset so that a worker can understand the voice message even in the presence of high ambient noise. 2023345418   13 Jul 2026 According to the invention, the controlled output unit in the control center is capable of outputting signals from the or each monitored workplace, namely in at least one form that can be perceived by a human. The controlled output unit generates a representation for each monitored workplace. These signals each 5 include an image signal from the or each camera in or at that workplace, and an alarm from the or each gas measuring device. Optionally, these signals further include target gas concentrations measured by the gas measuring device and / or voice messages from a person at the workplace and the number of people currently at the workplace. The central output computer is capable of 10 controlling the output unit. In a preferred embodiment, the output unit comprises an overview screen and at least one further screen for a visual output of image signals and optionally of further signals. Each screen can be controlled by the central output computer. The controlled overview screen is capable of simultaneously visually displaying the image signals from at least two cameras -15 of course only if these two cameras simultaneously generate image signals and are each in a data connection with the central output computer. The two cameras can be installed in or at the same workplace and belong to one and the same monitoring unit. They can also belong to two different monitoring units for two different monitored workplaces. In particular, thanks to the overview 20 screen, the operator can visually monitor several workplaces at the same time. The central output computer can control the overview screen. The overview screen is controlled in such a way that one respective area of the overview screen is used for each monitored workplace. The representation for this workplace is output in this screen area. For n monitored workplaces, therefore, 25 one respective representation is output in each of n screen areas. In particular, the respective image signal of the or each camera at the workplace is output in this screen area. Preferably, this screen area also shows in a visually perceptible way whether the or at least one gas measuring device at the monitored workplace is currently generating an alarm or not. 30 In one implementation, the or each additional screen is connected to the overview screen by means of a hinge, such as the two wings of an altarpiece. 2023345418   13 Jul 2026 This embodiment makes it possible to fold two screens together and then transport them. The or at least one other controlled screen can output information about one workplace at a time. This workplace was previously selected. It is also possible 5 that a gas measuring device at this workplace is currently generating an alarm. Preferably, the controlled further screen continues to output information about this workplace until another workplace is selected or the output of information is terminated. In one embodiment, the operator in the central output computer has selected 10 this workplace. In another embodiment, the central output computer has received an alarm from the or a gas measuring device or from the workplace computer or from another device in or at that workplace, and based on that alarm, the workplace is automatically selected. Preferably, the information about the workplace that is output to the further screen comprises the or at least one 15 target gas concentration that the gas measuring device has measured and that is above the specified concentration threshold. This target gas concentration thus triggered the alarm. The alarm and a message with the target gas concentration were transmitted from this workplace to the control center, whereby the alarm was preferably transmitted with a higher priority. Thus, on 20 the further screen, information about this workplace with the alarm is output. This embodiment makes it easier for the operator to determine the cause of an alarm and trigger appropriate action. Preferably, the information output also includes the or at least one image signal from a camera at this workplace and / or the number and / or the names of the persons who are at this workplace 25 according to the signals from the access control unit. According to the invention, the or each gas measuring device or the workplace computer of a monitoring unit is capable of automatically generating an alarm if the or a measured target gas concentration is above a concentration threshold specified for this target gas. This concentration threshold is preferably stored in 30 a data memory of the gas measuring device. This alarm is transmitted to the central output computer. In one embodiment, the central output computer is 2023345418   13 Jul 2026 able to control the output unit in response to the receipt of an alarm in such a way that the following is effected: The controlled output unit outputs a list, visually or in another form perceptible by a human. The outputted list specifies the workplace to which the alarm relates, that is, the workplace at or in which 5 the gas measuring device that generated the alarm is positioned. Further, the list specifies at least one action, preferably any action, to be taken in response to the alarm at the workplace. This embodiment facilitates an operator to then trigger quickly the or each required action when an alarm is generated and issued at the control center. The risk is reduced that a required action is not 10 taken at all or is taken too late. In one implementation, the list additionally comprises for at least one, preferably for each, action named in the list a respective input field. By making an input in this input field, the operator triggers, in one implementation, the action issued and to be performed without necessarily having to perform any further action. In 15 another implementation, the operator confirms having triggered the action by making an input. Preferably, the central output computer generates a message to the operator if the operator has not yet entered a confirmation for an action mentioned in the list. Further above, an embodiment was described in which the output unit 20 comprises an overview screen and at least one further screen. Preferably, the list just described is output on the or a further screen. It is possible for the output unit to include two additional screens. This allows two different workplaces to be selected simultaneously. This is particularly advantageous if a respective gas measuring device or other device has 25 generated an alarm almost simultaneously at each of two different workplaces. Particularly preferably, a respective list is displayed on a further screen for each selected workplace. An arrangement has already been described above in which to each monitored workplace on the overview screen a respective screen area is assigned. The 30 display for the workplace is output in this screen area. This representation comprises the respective image signal from the or each camera at the 2023345418   13 Jul 2026 workplace. In addition, the representation is output in a first manner when a gas measuring device or the workplace computer generates an alarm for that workplace, and in a second manner when neither a gas measuring device nor the workplace computer generates an alarm. For example, the image signal is 5 surrounded by a frame, and the frame differs in a visually perceptible manner depending on whether an alarm is generated or not. This frame visually separates the screen area for a workplace from the or any other screen area on the overview screen. The embodiment with the screen areas makes it easier for the operator to find 10 workplaces with alarms and associate at a glance the image signals with the alarms. This embodiment can be combined with the embodiment described further above in which a list is displayed on another screen, the list relating to a workplace at which an alarm is generated. The combination of these two embodiments makes it easier for a user to associate the list with the image 15 signal. The combination thus results in a particularly ergonomic configuration for monitoring. Preferably, the or at least one workplace computer, and particularly preferably each workplace computer, comprises its own voltage supply unit. This configuration avoids the need to connect the workplace computer to a stationary 20 power supply network. In many applications, this is not even possible or undesirable, especially because a long cable to the monitored workplace would be too dangerous. In addition, in some applications the workplace computer is intended to meet explosion protection requirements. On the one hand, it is usually desired that this dedicated voltage supply unit 25 supplies the workplace computer with electrical energy for as long as necessary. On the other hand, it is often desired that the voltage supply unit is relatively small and light, especially such that it can be easily transported to the workplace and / or detachably attached to the workplace. The latter constraint limits the electrical work that the voltage supply unit can provide. In addition, the 30 own voltage supply unit should often be an intrinsically safe device. The 2023345418   13 Jul 2026 following preferred implementation of a dedicated voltage supply unit meets these requirements. According to this implementation, the voltage supply unit of the workplace computer comprises an internal voltage source and at least one external 5 voltage source. Each voltage source is capable of supplying the or each electrical consumer of the workplace computer, optionally also a connected sensor, with electrical energy. Preferably, each voltage source is rechargeable. Preferably, the workplace computer with the internal voltage source and the or each external voltage source are configured as intrinsically safe devices. 10 The internal voltage source is located in a housing of the workplace computer and is thus protected to a certain extent from external influences. The or each external voltage source is detachably connected to the workplace computer or can be detachably connected to it. In many cases, an external voltage source can thus be replaced during operation, i.e. in or at the monitored workplace, i.e. 15 replaced by a new one. Replacement is particularly necessary when the previously used external voltage source is largely discharged. Often, monitoring of the workplace need not be interrupted to replace the external voltage source. If the workplace computer and each external voltage source are configured as intrinsically safe devices, the replacement can even be carried out in a 20 potentially explosive environment. As long as possible, the or each electrical consumer of the workplace computer and each connected consumer is supplied with electrical energy from the or a connected external voltage source. "As long as possible" means: as long as the level of the external voltage source is greater than or equal to a specified first 25 level threshold. The or each electrical consumer of the workplace computer is supplied from the internal voltage source only if no external voltage source is connected or if the or each connected external voltage source has a level below the first level threshold. The internal voltage source thus acts as a kind of buffer storage for electrical energy. One reason for preferring to use an external 30 voltage source is the following: While an external voltage source can often be replaced during operation, it is usually not possible to replace or recharge the 2023345418   13 Jul 2026 internal voltage source during operation, especially if the workplace computer is used in a potentially explosive environment. This is usually true even if the workplace computer is configured as an intrinsically safe device. At least, however, the exchange of the internal voltage source takes longer than the 5 connection to another external voltage source. Preferably, a signal-processing control unit of the workplace switches between a supply from the or an external voltage source and a supply from the internal voltage source. Preferably, the control unit repeatedly checks whether at least one external voltage source with a sufficient level is connected and then, if this 10 is the case, switches to this external voltage source. Preferably, the workplace computer generates a message when the level of the or a connected external voltage source has fallen below a specified second level threshold. The second level threshold is greater than or equal to the first level threshold. The message is output in a form that can be perceived by a 15 human, for example on an output element of the workplace computer itself or on the output unit of the control center. As the second level threshold is greater than the first level threshold, more time is available to replace the external voltage source without having to use the internal voltage source. This is because the low level message is output before the level reaches the first level 20 threshold. In one embodiment, the workplace computer can be connected to at least two external power sources simultaneously. This allows the workplace computer to be used for a longer duration without having to replace an external voltage source. Preferably, the or each electrical consumer is powered from a first 25 external voltage source until the level of the first external voltage source has dropped below the first level threshold. Preferably, the second external voltage source is not used as long as the level of the first external voltage source is high enough. Subsequently, the electrical consumers are supplied from the or a second external voltage source. The time span that elapses until the level of the 30 second external voltage source has also fallen below the first level threshold is available for replacing the first external voltage source. 2023345418   13 Jul 2026 Preferably, the communication unit also comprises its own voltage supply unit. This can be constructed in exactly the same way as the one just described with reference to the workplace computer. In one embodiment, the or each camera and / or the or each gas measuring 5 device of a monitoring unit each comprises its own respective voltage supply unit. This voltage supply unit can be configured as just described with reference to the workplace computer. It is also possible that at least one gas measuring device and / or at least one camera and / or an optional further device of the monitoring unit is supplied with electrical power by the workplace computer. The 10 or at least one camera is thus an electrical consumer that is supplied with electrical energy at least temporarily by the workplace computer. These two implementations can be combined with each other. This combination makes it possible for the workplace computer to supply electrical energy to at least one further device of the monitoring unit by means of a cable, if this further device is 15 arranged close enough to the workplace computer, but the further device can also be positioned at a distant location. It is also possible that a device at the workplace can be supplied either by the workplace computer or by its own voltage supply unit. It is also possible that the or at least one gas measuring device is supplied with 20 electrical energy by the workplace computer. According to the invention, the monitoring system comprises a communication unit and for each monitored workplace one respective monitoring unit. In a preferred embodiment, n workplaces are monitored simultaneously, where n >= 2. The monitoring system comprises at least n monitoring units, each with a 25 workplace computer, at least one camera and at least one gas measuring device. Preferably, the same communication unit is connected to each of these n workplace computers. This embodiment saves equipment compared to an embodiment in which a separate communication unit is used for each monitored workplace. The embodiment also saves data connections compared to an 30 embodiment in which each workplace computer or even each sensor is connected directly to the central output computer. It is sufficient to establish an 2023345418   13 Jul 2026 at least partially wireless data connection between the communication unit and the central output computer. According to a further implementation of this embodiment, at least two workplace computers and the communication unit are connected in series 5 ("daisy chain") as follows: A first data connection is established or can be established at least temporarily between the workplace computer of the first monitoring unit and the communication unit. A second data connection is established or can be established at least temporarily between the workplace computer of the second monitoring unit and the workplace computer of the first 10 monitoring unit. Signals from the other devices of the second monitoring unit are transmitted to the communication unit as follows: from the device at the workplace to the workplace computer of the second monitoring unit, from there via the second data connection to the workplace computer of the first monitoring unit, and from there via the first data connection to the communication unit. 15 Optionally, all n workplace computers for the n simultaneously monitored workplaces and the communication unit are connected in series. Signals from a sensor are thus forwarded through this series to the communication unit and from there to the central output computer. In many cases, the configuration with the series connection requires fewer data connections than other types of 20 circuits, for example less than a star connection. In order to be able to monitor a workplace remotely, it is necessary that a data connection is established between the devices of a monitoring unit and the central output computer. It must be possible to quickly detect the undesired event that during monitoring this data connection is interrupted. In one 25 embodiment, the central output computer generates for each monitored workplace a respective request message. Preferably, this request message is generated repeatedly, for example at fixed time intervals. The central output computer triggers the step of transmitting the request message for a workplace to the workplace computer of that workplace. In response to receiving the 30 request message, the workplace computer generates a response message. This response message is transmitted to the central output computer. The central output computer checks whether a response message arrives from a 2023345418   13 Jul 2026 workplace computer within a specified time period after the request message is sent to that workplace computer. If this is not the case, the central output computer generates an alarm and outputs this alarm in at least one form that can be perceived by a human. 5 Preferably, the reverse sequence is performed additionally or instead. The or each workplace computer generates a request message at least once, and the generated request message is transmitted to the central output computer. The central output computer generates a response message that is transmitted to the workplace computer. If the workplace computer has sent a request 10 message but has not received a response message from the central output computer within a specified time period, the workplace computer generates a warning and outputs it to the workplace in a form that can be perceived by a human. This warning warns the people at the workplace that the workplace is currently not monitored. 15 These two embodiments may be combined, for example as follows: In response to receiving a response message, the central output computer generates an acknowledgement message. This acknowledgement message is transmitted to the workplace computer from which the response message originated. If the workplace computer does not receive an acknowledgement message from the 20 central output computer within a specified time period after the response message is sent, the workplace computer generates an alarm and outputs it in a form that can be perceived by a human. In the following, the invention is described by means of an embodiment 25 example. The following is shown: Figure 1         two monitoring units and the communication unit; Figure 2 the communication unit and a mobile network that realizes a data connection via a central computer; 2023345418   13 Jul 2026 Figure 3 a first control center and a second control center and their respective connections to the mobile network; Figure 4 a workplace computer of figure 1 with one internal voltage source and two external voltage sources; Figure 5 a housing and a trolley for transporting the rest of the equipment of the control center; Figure 6 the support of the housing and several devices of the control center on this support; Figure 7 the overview screen on the support and two other screens. Application of the invention In an embodiment, the invention is used to remotely monitor at least one spatial area while work is being performed in or on that area. The area to be monitored 5 is hereinafter referred to as the "workplace". In particular, the workplace may be an enclosed space, such as the interior of a container for fluids or a warehouse or a space of a land vehicle, aircraft, or watercraft. A person performing at least one job at this workplace, for example, a welding job, is referred to as a "worker". 10 The or a workplace may leak gases that are harmful to a person. In addition, a worker may suffer an accident or a fainting spell. It is also possible that a worker is not wearing the safety equipment that is required for that workplace. Therefore, while the worker or at least one worker is working in the workplace, a human is remotely monitoring the workplace. This monitoring human is referred 15 to below as the "operator." The area where this operator monitors the workplace is referred to as the "control center". The system that supports the operator in remotely monitoring the workplace, optionally several workplaces simultaneously, is called a "monitoring system". It is possible that the same operator monitors at least two workplaces 20 simultaneously. 2023345418   13 Jul 2026 Components of the monitoring system The monitoring system includes - one component per monitored workplace, which is set up in or at this workplace, 5   - a component in the control center and - a communication unit (router) for bidirectional data transmission between the component at the workplace and the component in the control center. The component of the monitoring system that is set up in or at the workplace is hereinafter referred to as the "monitoring unit". 10 Figure 1 shows schematically - two monitored workplaces A.1, A.2, - for each monitored workplace A.1, A.2 one respective monitoring unit 100.1, 100.2, and - a communication unit ("router") 10. 15 Both workplaces A.1, A.2 are arranged in a respective enclosed space. Figure 1 schematically shows two entrances E.1, E.2 to the two workplaces A.1, A.2. A monitoring unit 100.1, 100.2 comprises - at least one camera, optionally several cameras, directed at the workplace, in case of several cameras preferably with different viewing directions, 20   - at least one gas measuring device, optionally several gas measuring devices, preferably for different target gases, - optionally at least one further sensor, for example a temperature sensor, - a workplace computer, - optionally an access control unit ("Badge-In / Badge-Out"), 25   - optionally a voice input unit comprising a microphone, - optionally a voice output unit comprising a loudspeaker, - optionally an alarm input element ("alarm button"), - optionally an alerting element ("siren"). 2023345418   13 Jul 2026 Figure 1 shows the following devices, which in the embodiment example belong to the monitoring unit 100.1 for the workplace A.1: - two gas measuring devices 1.1 and 1.2, - a camera 2.1, 5   - an optional temperature sensor 13.1, which is attached to the gas measuring device 1.1, - a workplace computer 3.1, - a voice input unit 4.1, - a voice output unit 5.1, 10   - an access control unit 6.1, and - an alarm input element 7.1. In the implementation shown, the workplace computer 3.1 and the gas measuring device 1.2 are arranged outside the enclosed space A.1, while the other devices are each arranged on the inside against a respective wall in the 15 enclosed space. A hose 8 is led from the gas measuring device 1.2 into the enclosed space A.1. The gas measuring device 1.2 can suck in a gas sample through the hose 8 out of the enclosed space A.1. It is also possible that all the devices of the monitoring unit 100.1 are arranged inside the enclosed space A.1. It is also possible that the workplace computer 3.1 is arranged inside the 20 enclosed space A.1. This has the advantage that a user can read an indicator light of the workplace computer 3.1 and / or actuate an actuating element without leaving the enclosed space A.1. On the other hand, in many cases the workplace computer 3.1 must then meet higher explosion protection requirements. 25 Figure 1 shows the following devices, which in the embodiment example belong to the monitoring unit 100.2 for the workplace A.2: - a gas measuring device 1.3, which is mounted inside on a wall of the workplace A.2, - a gas measuring device 1.4 placed on the floor outside the workplace A.2 30 and in front of the entrance E.2, - a camera 2.2 mounted inside on a wall of the workplace A.2, 2023345418   13 Jul 2026 - a camera 2.3 mounted inside on the ceiling of the workplace A.2, - an optional temperature sensor 13.2, - a workplace computer 3.2, - a voice input unit 4.2, 5   - a voice output unit 5.2, - an access control unit 6.2, and - an alarm input element 7.2. Again, the workplace computer 3.2 is arranged outside the monitored workplace A.2, the other devices in the workplace A.2. It is also possible that a workplace 10 computer 3.1 or 3.2 is arranged in the workplace A.1, A.2. In the embodiment shown in Figure 1, the gas measuring devices 1.1 and 1.2, the temperature sensor 13.1, the camera 2.1, the voice input unit 4.1, the voice output unit 5.1, and the alarm input element 7.1 are connected wirelessly, in particular by radio waves, to the workplace computer 3.1. The gas measuring 15 device 1.3, the cameras 2.2 and 2.3, the voice input unit 4.2, the voice output unit 5.2, and the alarm input element 7.2 are wirelessly connected to the workplace computer 3.2. This makes it easier to position each device at a suitable place in or at the monitored workplace A.1, A.2. In another implementation, the camera 2.1, the voice input unit 4.1, the voice 20 output unit 5.1, the access control unit 6.1, and / or the alarm input element 7.1 are supplied with electrical power by the workplace computer 3.1. It is possible that the camera 2.1, the voice input unit 4.1, the voice output unit 5.1, the access control unit 6.1, and the alarm input element 7.1 are detachably inserted, for example screwed, into a housing of the workplace computer 3.1. 25 Preferably, each camera 2.1, 2.2, 2.3 comprises its own light source to illuminate the workplace A.1, A.2. It is possible that the light source is permanently switched on and permanently illuminates the workplace A.1, A.2. It is also possible that a worker at the workplace A.1, A.2 or an operator in the control center switches the light source on and off. 2023345418   13 Jul 2026 Preferably, each workplace computer 3.1, 3.2 comprises indicator lights and control elements. In one embodiment, each workplace computer 3.1, 3.2 additionally comprises an output unit on which alarms from a connected gas measuring device 1.1, ..., 1.4 are output, preferably visually. 5 The part of the monitoring system installed in the control center includes - an overview screen, - optionally at least one additional screen, - optionally a voice output unit comprising a headphone, - optionally a voice input unit comprising a microphone, 10   - a central output computer, and - another communication unit. Figure 2 and Figure 3 schematically show the communication unit 10, a first control center Z and a second control center T. The communication unit 10 is connected or can at least temporarily be connected to the control centers Z and 15 T via the schematically shown Internet I. The connection via the Internet I implements a bidirectional wireless data connection. This data connection is established with the aid of a central computer 15. The communication unit 10 is located outside the workplaces A.1 and A.2 and therefore does not necessarily need to meet such high explosion protection requirements as the equipment in 20 a workplace A.1, A.2. The following devices of the first control center Z are shown: - a central output computer 20, which in the embodiment takes the form of a laptop computer with its own screen, a mouse 50, and its own keyboard, - a separate communication unit (router) 47, 25  - headphones 21, - a microphone 27 attached to the headphones 21, - an overview screen 22, - two further screens 23.1, 23.2, which in one implementation are movably connected to the overview screen 22 and which are in another 30 implementation adjacent to the overview screen 22, and 2023345418   13 Jul 2026 - an output program 48, such as a web browser, installed on the central output computer 20. The headphones 21, microphone 27, and screens 22, 23.1, 23.2 are each in a data connection with the central output computer 20. The output program 48 is 5 installed on the central output computer 20 and is executable there. The central output computer 20 may also include a separate keyboard and / or additionally a mouse 50. Two windows 24.1 and 24.2 are shown on the overview screen 22. The window 24.1 shows an image sequence A.1' from the workplace A.1, the window 24.2 10 shows an image sequence A.2' from workplace A.2. A frame 27.1 is arranged around the window 24.1, and a frame 27.2 is arranged around the window 24.2. The second control center T is implemented by means of a tablet Tb. This tablet Tb acts as the second central output computer and includes a screen 28 and is connected or connectable to the headphones 21. The headphones 21 are 15 connected to a microphone 27. An output program 49, such as a web browser, is installed on the tablet Tb. The screen 28 of the tablet Tb also displays two windows 24.1 for the workplace A.1 and 24.2 for the workplace A.2. The central output computer 20, Tb is able to control the or each screen 22, 23.1, 23.2 as well as the headphones 21. For this purpose, the central output 20 computer 20, Tb uses an output program 48, 49 and the processing 17 described above, which was generated by the central computer 15. Optionally, an image evaluation unit is installed on the central output computer 20. This image evaluation unit automatically evaluates image signals from at least one camera, preferably from each camera 2.1, 2.2, 2.3. One objective of the 25 evaluation is to detect whether or not the images from a workplace A.1, A.2 show at least one moving person. In some cases, the image evaluation can also detect an undesired event, for example a fire. In one embodiment, the entire part of the monitoring system installed in the control center is implemented on a portable computer, in particular on a 30 smartphone or tablet. Corresponding components of the portable computer act 2023345418   13 Jul 2026 as the overview screen, the voice output unit, the voice input unit, and the central output computer. This is exemplified in Figure 3 for the second control center T on the tablet Tb. Functions of the devices of a monitoring unit 5 The functions of these devices are described below. The or each gas measuring device 1.1, 1.2, 1.3, 1.4 measures the concentration of at least one target gas at the monitored workplace A.1, A.2, optionally the respective concentration of several target gases, and compares the or each measured target gas concentration with a respective specified 10 upper concentration threshold. If the or a target gas concentration is above the upper concentration threshold, the gas measuring device 1.1, 1.2, 1.3, 1.4 automatically generates an alarm. The measured target gas concentrations and alarms are transmitted to the control centers Z, T and output in at least one way that can be perceived by a human. It is also possible that only the measured 15 target gas concentrations are transmitted to the control centers Z, T, and the output computer 20 evaluates the transmitted measured values and generates the alarms. In one embodiment, the or at least one gas measuring device 1.1, 1.3, 1.4 is located in or in front of the monitored workplace A.1, A.2, and gas diffuses into 20 the interior of the gas measuring device 1.1, 1.3, 1.4 or is sucked in, e.g. by a pump of the gas measuring device 1.1, 1.3, 1.4. In another embodiment, at least one gas measuring device 1.2 is connected to a hose 8. The hose 8 is led into the interior of a workplace A.1 having the form of an enclosed space. The gas measuring device 1.2 is arranged outside this enclosed space A.1 and 25 permanently sucks in gas from the space through the hose 8, preferably with its own pump. This means that the gas measuring device 1.2 is not exposed to mechanical and chemical influences in the enclosed space A.1. The temperature sensor 13.1, 13.2 measures an indicator for the temperature at the monitored workplace A.1, A.2. In one embodiment, the temperature sensor 30   13.1, 13.2 is capable of automatically generating an alarm if the 2023345418   13 Jul 2026 measured temperature is outside a specified value range. This alarm indicates that it is too hot or too cold at the monitored workplace. The or each camera 2.1, 2.2, 2.3 generates a respective image signal, preferably a sequence of images, from the workplace A.1, A.2. The or each 5 image signal from a camera 2.1, 2.2, 2.3 is transmitted to the control centers Z, T and displayed there in each case on the or at least one screen. In one embodiment, at least one camera 2.1, 2.2, 2.3 has a light source, wherein this light source is configured to illuminate the monitored workplace A.1, A.2. Preferably, the light source emits light in the visible range, but it may 10 also emit light in the infrared range. In one embodiment, this light source can be switched on and off by an external control. In one embodiment, each camera 2.1, 2.2, 2.3 can be switched on and off by a control from the outside to save energy. Preferably, the or each camera 2.1, 2.2, 2.3 each has at least one, preferably 15 several parameters whose respective value can be changed by an external control. Examples of these parameters are: - the frame rate ("frames per second"), - the resolution, i.e. the number of pixels per image, - another parameter that affects the amount of data per unit time required to 20 transmit an image signal from camera 2.1, 2.2, 2.3, - the viewing direction, the viewing angle, the magnification, and whether the optional light source is switched on or off. In one embodiment, each camera 2.1, 2.2, 2.3 is configured during use in such a way that the viewing direction remains constant as long as the camera is 25 mounted in or at the workplace A.1, A.2. In another embodiment, an actuator is assigned to at least one camera. This actuator is capable of moving the camera 2.1, 2.2, 2.3 and thereby changing the viewing direction of the camera 2.1, 2.2, 2.3. Preferably, this actuator can be controlled from the outside. In one embodiment, each camera 2.1, 2.2, 2.3 has a fixed focal length and thus 30 a fixed mapping scale. In another embodiment, the focal length and thus the 2023345418   13 Jul 2026 mapping scale of the camera 2.1, 2.2, 2.3 can be changed, preferably by an external control. In a preferred implementation, each camera 2.1, 2.2, 2.3 comprises a photosensor, its own image processor and its own control unit, and optionally 5 also its own voltage supply unit. The photosensor is capable of generating digital images in response to electromagnetic waves, in particular light rays, impinging on the camera 2.1, 2.2, 2.3. In one embodiment, the configuration of the camera 2.1, 2.2, 2.3 determines how many pixels a digital image has. In another embodiment, the resolution can be changed by an external control. The 10 frame rate is the frequency at which the photosensor generates and delivers digital images. If the frame rate is too low, the undesirable event of the image signal being displayed on a screen in a jerky manner may occur. The image processing unit generates an image signal from the sequence of digital images generated by the photosensor. Preferably, the image processing 15 unit applies a compression algorithm. In order to transmit this image signal to a spatially distant receiver, an amount of data per time unit (bit rate) is required. This required bit rate depends on the image processing unit, in particular on the applied compression algorithm. At least one parameter influences the function of the image processing unit. This parameter is in particular a parameter of the 20 compression algorithm. A very strong compression may result in details in a visual representation of the image signal not being recognizable. The image processing unit parameter usually affects the bit rate required to transmit the image signal from the camera 2.1, 2.2, 2.3. It is possible that there are several such parameters that influence the compression algorithm and can be changed 25 independently of each other. A worker can enter a voice message into the voice input unit 4.1, 4.2 at the workplace A.1, A.2. This voice message is output to the operator by the voice output unit 21 in the control centers Z, T, preferably via the headphones 21. Accordingly, the operator can input a voice message, and this voice message is 30 transmitted and output to the worker, preferably via the loudspeaker 5.1, 5.2. This allows the worker and the operator to exchange voice messages. 2023345418   13 Jul 2026 When a worker enters the workplace A.1, A.2, he or she logs in at the access control unit 6.1, 6.2, for example by holding an RFID chip on a card against an RFID reader of the access control unit 6.1, 6.2. When he or she leaves the workplace A.1, A.2 again, he or she logs out in the same way. When a person 5 logs in, the access control unit 6.1, 6.2 determines which person has logged in or logged out. In one implementation, the workplace computer 3.1, 3.2 determines how many and what persons are currently at the workplace A.1, A.2 according to the access control unit 6.1, 6.2. This information is transmitted to the central control units Z, T, where it is output in a form that can be perceived 10 by a human being. In another implementation, the respective identifier of a worker who has logged in or logged out is transmitted to the central output computer 20. The central output computer 20 uses this transmitted data to count how many workers are currently in or at the monitored workplace A.1, A.2. 15 It is possible that a worker enters the workplace A.1, A.2 without logging in on the access control unit 6.1, 6.2. It is also possible that the access control unit 6.1, 6.2 is defective or a data transmission is interrupted. For this reason, the workplace A.1, A.2 is preferably permanently monitored during the period in which work is or can be performed there. 20 The alerting element 7.1, 7.2 can be used by a worker to signal that an alarm is to be triggered at the workplace A.1, A.2 in a form that can be perceived by a human being. A corresponding alarm message is generated, transmitted to the control centers Z, T, and output to the operator. Preferably, a voice connection between the workplace A.1, A.2 and the control centers Z, T is also established 25 automatically. Data transmission within the monitoring unit The or each gas measuring device 1.1, 1.2, 1.3, 1.4 as well as the or each camera 2.1, 2.2, 2.3 and the or each optional temperature sensor 13.1, 13.2 are connected to the workplace computer 3.1, 3.2 by cable and / or wirelessly, in 30 particular by radio waves. As wireless data connection between the or a gas measuring device 1.1, 1.2, 1.3, 1.4 and the workplace computer 3.1, 3.2 2023345418   13 Jul 2026 preferably Bluetooth is used, for the or each camera 2.1, 2.2, 2.3 preferably WLAN, e.g. Wi-Fi, or also Bluetooth is used. Preferably, the workplace computer 3.1, 3.2 comprises several indicator lights in the form of LEDs. Some of these indicator lights indicate whether or not a data 5 connection is currently established between the workplace computer 3.1, 3.2 and the other devices of the monitoring unit 100.1, 100.2. In addition, the workplace computer 3.1, 3.2 preferably comprises a relatively small screen on which error messages and other status messages are output, for example the current level of a voltage supply unit for the workplace computer 3.1, 3.2 and / 10 or information about which persons are currently at the workplace A.1, A.2 according to signals from the access control unit 6.1, 6.2. Optionally, an alarm from a connected gas measuring device 1.1, 1.2, 1.3, 1.4 is also output on this screen. In one embodiment, the workplace computer 3.1, 3.2 automatically detects 15 whether a gas measuring device 1.1, 1.2, 1.3, 1.4 and / or a camera 2.1, 2.2, 2.3 are connected by means of a cable. If this is not the case, the workplace computer automatically establishes a wireless data connection via radio waves. In one embodiment, a gas measuring device 1.1, 1.2, 1.3, 1.4 and / or a camera 2.1, 2.2, 2.3 can be mechanically connected to the workplace computer 3.1, 3.2, 20 for example by means of a threaded connection or a plug connection. This connection can preferably be released again. In one embodiment, the or each camera 2.1, 2.2, 2.3 is connected to the associated workplace computer 3.1, 3.2 via a respective cable. On the one hand, the image signal from the camera 2.1, 2.2, 2.3 is transmitted to the 25 workplace computer 3.1, 3.2 via this cable. On the other hand, in one embodiment, the camera 2.1, 2.2, 2.3 is supplied with electrical power from the workplace computer 3.1, 3.2 via this cable. This embodiment eliminates the need to provide the camera 2.1, 2.2, 2.3 with its own voltage supply unit. It is also possible that the or each gas measuring device 1.1, 1.2, 1.3, 1.4 is 30 connected to the workplace computer 3.1, 3.2 via a respective cable and, on the 2023345418   13 Jul 2026 one hand, measured values of the gas measuring device 1.1, 1.2, 1.3, 1.4 are transmitted to the workplace computer 3.1, 3.2 via this cable. In one implementation, the workplace computer 3.1, 3.2 supplies the gas measuring device 1.1, 1.2, 1.3, 1.4 with electrical energy via the cable. 5 Preferably, on the other hand, the gas measuring device 1.1, 1.2, 1.3, 1.4 comprises its own voltage supply unit, and the measured values of the gas measuring device 1.1, 1.2, 1.3, 1.4 are transmitted wirelessly, in particular by radio waves, to the workplace computer 3.1, 3.2. In one embodiment, a camera 2.1, 2.2, 2.3 and / or a gas measuring device 1.1, 10   1.2, 1.3, 1.4 and / or the workplace computer 3.1, 3.2 are able to automatically detect whether they are connected to the workplace computer 3.1, 3.2 via a cable and whether or not electrical energy is being transmitted via this cable. If this is not the case, the camera 2.1, 2.2, 2.3 or the gas measuring device 1.1, 1.2, 1.3, 1.4 switches over to its own voltage supply unit, or the devices are 15 switched over accordingly by an external control. This embodiment further increases the flexibility of the monitoring system according to the invention. In particular, it is made possible to supply the camera 2.1, 2.2, 2.3 and / or the gas measuring device 1.1, 1.2, 1.3, 1.4 with electrical power from the workplace computer 3.1, 3.2 if the distance is short enough. On the other hand, it is 20 possible to mount the camera 2.1, 2.2, 2.3 and / or the gas measuring device 1.1, 1.2, 1.3, 1.4 at a relatively large distance from the workplace computer 3.1, 3.2 without the length of a cable limiting the distance to the workplace computer 3.1, 3.2. Preferably, the or each workplace computer 3.1, 3.2 checks whether or not 25 there is still a data connection to each further device of the monitoring unit 100.1, 100.2. Particularly preferably, the workplace computer 3.1, 3.2 regularly polls each connected device. If a device does not respond, the workplace computer 3.1, 3.2 preferably generates a corresponding alarm message. The alarm message is transmitted to the central output computer 20, where it is 30 output in a form that can be perceived by a human. 2023345418   13 Jul 2026 Explosion safety As already explained, harmful gases can escape at a workplace A.1, A.2 to be monitored, in particular explosive gases. Therefore, all components of the monitoring unit 100.1, 100.2 for this workplace A.1, A.2 are preferably 5 configured as intrinsically safe devices. In one implementation, each device has a certification according to ATEX and / or IECEx and / or fulfills the standard ISO 80079-36 and -37, thus fulfilling a relatively high requirement for explosion protection. In the case of an intrinsically safe device, the electrical current and the electrical power are limited at all times by suitable components in the 10 device. This means that the device cannot trigger an explosion in any situation or under any operating conditions. In particular, the device does not generate any sparks that could escape to the outside and cause an explosion. In addition, an intrinsically safe device does not heat up to the point where the heated device can cause an explosion. 15 The configuration as an intrinsically safe device eliminates the need to surround the device with a flameproof housing made of metal and to separate the device fluid-tight from the environment. This would often not be possible at all for a gas measuring device, for example, and would also significantly increase the weight of the device. 20 Configuration of the monitoring unit as a portable unit In the embodiment example, the workplace A.1, A.2 does not need to be permanently monitored, but only during a period in which at least one worker performs work there. Outside this period, no one is present at or in the workplace A.1, A.2. Before the start of the work to be monitored, a monitoring 25 unit 100.1, 100.2 is set up at and / or in the workplace A.1, A.2 to be monitored, a data connection is established with the control center Z, T, and the workplace A.1, A.2 is monitored in the control centers Z, T. After the end of the monitoring, the devices of the monitoring unit 100.1, 100.2 are disconnected from each other again. Because all devices of a monitoring unit 100.1, 100.2 are 30 configured as intrinsically safe devices, it is possible to assemble the devices at or in the workplace A.1, A.2 to be monitored to create the monitoring unit 100.1, 2023345418   13 Jul 2026 100.2 itself and to disassemble them from each other again later. Of course, it is also possible to assemble the devices outside the workplace A.1, A.2 to the monitoring unit 100.1, 100.2 and to transport the monitoring unit 100.1, 100.2 into the workplace A.1, A.2. 5 Preferably, the devices of a monitoring unit 100.1, 100.2 are configured as portable devices. Therefore, in many cases neither a vehicle nor a crane is required to transport the devices to the workplace A.1, A.2. Particularly preferably, the summed weight of all devices of a monitoring unit 100.1, 100.2 is below 20 kg, particularly preferably below 10 kg. Therefore, a single person can 10 carry all devices of a monitoring unit 100.1, 100.2 to the workplace A.1, A.2 to be monitored and assemble them there. The fact that each device of a monitoring unit 100.1, 100.2 is designed as an intrinsically safe device and therefore does not necessarily have a flameproof housing contributes to this result. Such a flameproof housing often has a relatively high weight. 15 It is also possible that a person in the vicinity of the workplace A.1, A.2 to be monitored assembles the devices to the monitoring unit 100.1, 100.2 and carries the assembled monitoring unit 100.1, 100.2 to the workplace. Preferably, no aids at all or only common tools are required for assembling the devices to the monitoring unit 100.1, 100.2. 20 In one embodiment, the devices belonging to a monitoring unit 100.1, 100.2 are placed on the floor at or in the workplace A.1, A.2. In a preferred embodiment, however, they are detachably fixed. In particular, a device of a monitoring unit 100.1, 100.2 can be detachably attached to a component of the workplace A.1, A.2 in one of the following alternative implementations: 25   - The device to be fixed includes at least one permanent magnet, and the magnet is placed on a sufficiently large vertical or inclined magnetic surface of the workplace A.1, A.2. - The device includes a clamp fastening (mounting) with a mounting plate. This clamp fastening is detachably mounted in a suitable recess or on a 30 suitable mounting element of the workplace A.1, A.2. 2023345418   13 Jul 2026 - The device includes a fastening element with which the device can be detachably fastened to a flange connection. Such a flange connection is often located at a monitored workplace A.1, A.2. - The device comprises a suction element, in particular a suction cup. This 5 suction element is pressed onto a sufficiently large, load-bearing and clean surface at the workplace A.1, A.2. Preferably, at least one device comprises at least two of these possible fastening elements, i.e. a permanent magnet and / or a clamp fastening and / or a fastening element for a flange connection and / or a suction element, so that 10 in many cases the device can be detachably fastened in at least one, preferably at least two, of the ways just described and need not be placed on the ground. Data transmission between the monitoring unit and the control center On the one hand, the communication unit 10 is in a bidirectional data connection with the workplace computer 3.1, 3.2 of a monitoring unit 100.1, 15   100.2. On the other hand, the communication unit 10 is in a bidirectional data connection with the central output computer 20. The same communication unit 10 can simultaneously be in a respective bidirectional data connection with at least two workplace computers 3.1, 3.2, see Figure 1. The or each connected workplace computer 3.1, 3.2 is connected to the 20 communication unit 10 via cable or wirelessly, in particular via Wi-Fi. In one embodiment, a 10 Mbit or 100 Mbit Ethernet connection can be established using the cable. In one embodiment, the communication unit 10 is able to automatically detect whether a workplace computer 3.1, 3.2 is connected to the communication unit 10 by means of a cable. If the communication unit 10 25 detects a connected cable, data is exchanged between the workplace computer 3.1, 3.2 and the communication unit 10 via this cable, otherwise wirelessly, in particular via radio waves. It is possible that the communication unit 10 additionally supplies a workplace computer 3.1, 3.2 with electrical energy via a cable. 30 In one embodiment, the communication unit 10 is also detachably mounted, and particularly preferably in the vicinity of the or a monitored workplace A.1, A.2. 2023345418   13 Jul 2026 The mounting elements described above with reference to the devices of the monitoring unit 100.1, 100.2 can also be used for the communication unit. As already explained, it is possible to connect the same communication unit 10 to at least two different workplace computers 3.1, 3.2 and thereby to at least two 5 different monitoring units 100.1, 100.2. Preferably, a series connection is implemented according to the "daisy chain" principle: A first workplace computer 3.1 is connected on the one hand to a second workplace computer 3.2 and on the other hand to the communication unit 10, cf. Figure 1. The series connection saves the need to realize a star connection and requires fewer data 10 connections. Preferably, signals are transmitted from the second workplace computer 3.2 via the first workplace computer 3.1 to the communication unit 10 and further to the control center Z, T, and vice versa, messages are transmitted from the control centers Z, T to the communication unit 10 and further via the first workplace computer 3.1 to the second workplace computer 3.2. This series 15 connection is indicated in Figure 1. In the embodiment, the communication unit 10 is wirelessly connected to the central output computer 20 and to the tablet Tb of the mobile control center T via the Internet I and a public mobile radio network, for example via LTE (Long Term Evolution) or 5G. Figure 2 schematically shows the Internet I, a central 20 computer 15, and a cloud through which the communication unit 10 is connected to both the stationary control center Z and the mobile control center T, cf. Figure 3. The two control centers Z, T are thus connected in parallel. In one embodiment, the central computer 15 receives the respective signals from the or each monitoring unit 100.1, 100.2 and stores them at least temporarily. 25 In the embodiment example, a monitoring system area 16 is provided on the central computer 15 and is used to monitor the two workplaces A.1, A.2. It is possible that the monitoring system area 16 is permanently assigned to the monitoring system according to the invention. Preferably, on the other hand, this monitoring system area 16 is used only for a specified time period to implement 30 functions of the monitoring system according to the invention. The work at the workplaces A.1, A.2 takes place within this specified time period. Of course, it is 2023345418   13 Jul 2026 possible to subsequently monitor at least one other workplace within this time period and to use the same monitoring system area 16 for this purpose. Preferably, at the end of this time period, the or each program and all data in monitoring system area 16 are deleted, and the monitoring system area is made 5 available for other applications. The monitoring system area 16 includes a processing program 18, for example a web server. This processing program 18 can be executed on the central computer 15, processes the signals from the devices at the workplaces A.1, A.2 during its execution, and generates a processing 17, which is a set of data that 10 can be output in a form that can be perceived visually and / or acoustically and / or haptically by a human. An output program 48, 49 is installed on the central output computer 20, in particular a web browser. The central output computer 20 receives the processing 17 from the central computer 15 via the Internet I and causes the output program 48, 49 to display the processing 17 in the first 15 control center Z. This will be described in more detail below. The tablet Tb of the second control center T receives the same processing 17 and displays it. The use of a public mobile radio network I has in particular the following advantages compared to the alternative of establishing a directional radio link: It is not necessary to ensure a permanent line of sight between the 20 communication unit 10 and the central output computer 20. Furthermore, in many cases it is not necessary to precisely align antennas of a workplace computer 3.1, 3.2 and / or the communication unit 10. Also, in many cases, a much greater distance can be bridged between the communication unit 10 and the control center Z, T. This provides greater flexibility as to where a control 25 center Z, T can be positioned relative to a workplace A.1, A.2 to be monitored. Furthermore, it is made possible to monitor several workplaces in one and the same control center Z, T, whereby these workplaces are relatively far away from each other. The or each workplace computer 3.1, 3.2 is capable of transmitting data from 30 the connected devices to the central computer 15. In one implementation, the central computer 15 regularly polls each workplace computer 3.1, 3.2. 2023345418   13 Jul 2026 In one embodiment, a web server is installed on the central computer 15. A display program in the form of a web browser 48 is installed on the central output computer 20, and a display program 49 is installed on the tablet Tb. In one embodiment, to the or each monitoring unit 100.1, 100.2 a respective 5 unique Internet address is assigned. In another implementation, a unique Internet address is assigned to the communication unit 10. In a preferred embodiment, a unique Internet address is assigned to the monitoring system area 16 on the central computer 15. After a user has entered this Internet address into the web browser 48, 49, the central computer 15 transmits the 10 above-described processing 17 of signals originating from the workplace computer 3.1, 3.2 of this monitoring unit 100.1, 100.2 or from the communication unit 10 to the central output computer 20 and to the tablet Tb, in particular image signals, alarms and other measurement results. This embodiment makes it possible to quickly establish a connection between the 15 central output computer 20 and the tablet Tb on the one hand and the central computer 15 on the other hand. At the beginning of an operation as well as during the operation, it must be ensured that a data connection is actually established between the or each monitoring unit 100.1, 100.2 and the control centers Z, T. If it is determined that 20 no data connection has been established between a monitoring unit 100.1, 100.2 and a control center Z, T, an alarm is automatically triggered and issued in at least one form that can be perceived by a human being, preferably both at the workplace A.1, A.2 by the monitoring unit 100.1, 100.2 as well as in the control center Z, T. Preferably, an alarm is also generated and output if a gas 25 measuring device 1.1, 1.2, 1.3, 1.4 or a camera 2.1, 2.2, 2.3 has failed. An alarm triggered at or for a workplace A.1, A.2 preferably includes information that this workplace A.1, A.2 is to be evacuated. Various configurations are possible for checking whether a data connection has been established and still exists between the control centers Z, T and a 30 workplace A.1, A.2. 2023345418   13 Jul 2026 In one embodiment, the or each workplace computer 3.1, 3.2 generates a message repeatedly in such a way that there is at most a specified time interval between the generation of two successive messages. For example, messages are generated with a fixed frequency. Each message is transmitted to the 5 control center Z, T. The central output computer 20, Tb in the control center Z, T detects the undesired event that there is no data connection between a workplace computer 3.1, 3.2 and the central output computer 20 or the tablet Tb when at least one of the following events is detected: - There is no message at all from a workplace 3.1, 3.2. 10   - The central output computer 20 / tablet Tb has received a message from a workplace computer 3.1, 3.2, and after this reception a time period of a specified duration has elapsed without another message having arrived from this workplace computer 3.1, 3.2. In a further embodiment, the central output computer 20 / the tablet Tb 15 repeatedly generates one message for each workplace computer 3.1, 3.2, again in such a way that there is at most the specified time interval between the generation of two successive messages. Each message is transmitted to the respective workplace computer 3.1, 3.2. The workplace computer 3.1, 3.2 detects the event that there is no data connection to a control center Z, T, if no 20 message at all has been received from the control center Z, T or if a time period has elapsed since the last message was received from the control center Z, T, which time period has a specified duration. The two embodiments just described can be combined. In a further embodiment, the following steps are performed at the beginning of a 25 deployment, and these steps are preferably performed again at least once during the deployment, preferably at a fixed frequency: - The central output computer 20 and the tablet Tb each generate a request message for each workplace 3.1, 3.2, and this request message is transmitted to the workplace 3.1, 3.2 via the central computer 15 and the 30 communication unit 10, unless a fault has occurred. 2023345418   13 Jul 2026 - As soon as the workplace computer 3.1, 3.2 receives this request message, it generates a response message. This response message is transmitted to the central output computer 20 and to the tablet Tb. - The central output computer 20 and the tablet Tb check whether or not a 5 response message has arrived from a workplace computer 3.1, 3.2 after the step of transmitting a request message to that workplace computer 3.1, 3.2 and after a specified time period has elapsed. If no response message has then arrived, the central output computer 20 / the tablet Tb generates an alarm referencing this workplace A.1, A.2. 10   - Conversely, if a workplace A.1, A.2 does not receive a request message after an activation, the workplace A.1, A.2 also preferably generates an alarm. This alarm indicates that the relevant workplace A.1, A.2 may currently not be monitored. Change in the required bandwidth 15 The wireless connection between the communication unit 10 and the control centers Z, T uses the Internet I and the public mobile network without influencing them. Therefore, this wireless connection strongly depends on the bandwidth that is currently available for data transmission between the communication unit 10 and the control centers Z, T. Different events in the 20 vicinity of a monitored workplace A.1, A.2 can cause other communication units to consume a lot of bandwidth and therefore greatly reduce the bandwidth that is still available for data transmission between the communication unit 10 and the control centers Z, T. If at all possible, monitoring of the or each connected workplace A.1, A.2 should be maintained despite changing bandwidth. 25 Most bandwidth is required to transmit the respective image signal from the or each camera 2.1, 2.2, 2.3 to the control centers Z, T. Much less bandwidth is required to transmit the respective signal and, if applicable, an alarm of each gas measuring device 1.1, 1.2, 1.3, 1.4. The event that only a lower bandwidth than before is available and / or the event that not enough bandwidth is 30 available is detected automatically. Preferably, the value of at least one 2023345418   13 Jul 2026 parameter of the data transmission that correlates with the available bandwidth is determined. In particular, the following parameters are examined: - the latency - if this is greater than a given upper threshold, there is too little bandwidth available, and / or 5   - the loss of data packets during transmission (packet loss and packet drop). As explained above, the image signal from the or each camera 2.1, 2.2, 2.3 at the monitored workplace A.1, A.2 requires the greatest bandwidth. Detection of insufficient bandwidth triggers the step of down-regulating the or each camera 2.1, 2.2, 2.3 currently providing an image signal to the communication unit 10. 10 The down-regulating of the camera 2.1, 2.2, 2.3 comprises the step that the camera 2.1, 2.2, 2.3 is externally controlled and by the control at least one bandwidth-relevant parameter of the camera 2.1, 2.2, 2.3 is assigned a different value, i.e. a parameter influencing the bit rate required to transmit the image signal from the camera 2.1, 2.2, 2.3 to the control centers Z, T. 15 In one implementation, the control changes at least one of the following parameters of a camera 2.1, 2.2, 2.3 with the objective of reducing the required bandwidth: - The resolution, i.e. the number of pixels per image, is reduced. - The frame rate, i.e. the number of images generated per second ("frames 20 per second"), is reduced. - The algorithm that the image processing unit applies to the images of the photosensor is modified in such a way that the images are more compressed and thus a single image takes up a smaller amount of data. Preferably, each camera 2.1, 2.2, 2.3 is configured in such a way that the 25 resolution, the frame rate, and the parameter for the image processing algorithm can be changed independently of each other by a corresponding external control. As already explained, according to a preferred implementation, each camera 2.1, 2.2, 2.3 comprises a photosensor and an image processing unit. The 30 photosensor generates a sequence of digital images at a variable frame rate 2023345418   13 Jul 2026 ("frames per second"). The image processing unit generates the image signal from the sequence of digital images. The image signal is transmitted to the control centers Z, T via the workplace computer 3.1, 3.2 and the communication unit 10. In order to transmit this image signal, a quantity of data per unit of time 5 (bit rate) is required. This bit rate is influenced by a variable parameter of the image processing unit, in particular by a parameter of a compression algorithm applied by the image processing unit. The resolution, the frame rate, and the parameter acting on the bit rate are three externally variable bandwidth-relevant parameters of the camera 2.1, 2.2, 2.3. 10 The step of assigning a possibly modified value to each of the parameters just mentioned and using it is automatically triggered and reduces the bandwidth required to transmit image data from the respective camera 2.1, 2.2, 2.3 to the communication unit 10 and further to the control centers Z, T via a public mobile radio network. Such an action is preferably triggered when an indication of low 15 bandwidth is detected. In one embodiment, at least one action to reduce the required bandwidth is also performed if at least one of the following events is detected: - According to the signal from the access control unit 6.1, 6.2, there is currently no worker in or at the monitored workplace A.1, A.2. Note: It is 20 possible that a worker is there, but has not registered with the access control unit 6.1, 6.2. Therefore, even in this situation, images are transmitted to the control units Z, T, and the camera 2.1, 2.2, 2.3 is not switched off. - An image processing unit (not shown) evaluates images from the camera 2.1, 2.2, 2.3 and has detected by the evaluation that there is no movement 25 in or at the workplace A.1, A.2, namely in a time period of a specified duration. Also in this situation, images continue to be transmitted to the control centers Z, T. - An operator in a control center Z, T has caused the value of a bandwidthrelevant parameter to be reduced for a camera 2.1, 2.2, 2.3. One reason 30 may be that the operator requires an image sequence from another camera 2.1, 2.2, 2.3, the transmission of which requires a higher bandwidth. 2023345418   13 Jul 2026 It is possible that at least two cameras 2.1, 2.2, 2.3 are connected to the same communication unit 10, for example because a monitoring unit 100.2 comprises two cameras or because two different monitoring units 100.1, 100.2 each comprising one camera 2.1, 2.2, 2.3 are simultaneously connected to the 5 communication unit 10, cf. Figure 1. In one embodiment, the at least two connected cameras 2.1, 2.2, 2.3 are down-regulated in the same way. In another embodiment, a request is made to the operator in one or each control center Z, T to select a connected camera 2.1, 2.2, 2.3. The or at least one selected camera 2.1, 2.2, 2.3 is down-regulated, or the or at least one 10 unselected camera 2.1, 2.2, 2.3 is down-regulated. Various embodiments are possible as to which person or device triggers the down regulation of a camera 2.1, 2.2, 2.3. As explained above, from a control center Z, T, the operator may trigger the step of down-regulating any camera connected to a user-selected workplace 3.1, 3.2 or a user-selected camera 2.1, 15   2.2, 2.3. Preferably, the operator is notified that there is not enough available bandwidth, and the operator selects at least one monitored workplace A.1, A.2. The workplace computer 3.1, 3.2 of the selected workplace A.1, A.2 then down-regulates the or at least one, preferably each camera 2.1, 2.2, 2.3 of the selected workplace A.1, A.2. 20 In one implementation, the central output computer 20 and the tablet Tb regularly query the central computer 15 as to which respective bandwidth is available for a data transmission from a workplace computer 3.1, 3.2 to the central output computer 20 or the tablet Tb. The central output computer 20 and the tablet Tb transmit the queried bandwidth to the workplace computer 3.1, 3.2. 25 It is also possible that at least one workplace computer 3.1, 3.2 regularly queries the central computer 15. In a preferred embodiment, a workplace 3.1, 3.2 is able to automatically detect that the available bandwidth is insufficient. Lack of bandwidth usually results from the fact that the used public mobile radio network I does not provide 30 sufficient bandwidth to transmit data from the communication unit 10 to the control centers Z, T. The connection between the workplace computer 3.1, 3.2 2023345418   13 Jul 2026 and the communication unit 10 is usually not affected by a low bandwidth, in particular not by a low bandwidth in the public mobile radio network I used. After the workplace computer 3.1, 3.2 has detected the low bandwidth for a workplace A.1, A.2, it controls the or at least one, preferably each connected 5 camera 2.1, 2.2, 2.3 at the workplace A.1, A.2 in order to down-regulate the camera 2.1, 2.2, 2.3 and thereby to reduce the required bandwidth. The process just described does not require message exchange between different workplace computers 3.1, 3.2, nor does it require message exchange between a workplace computer 3.1, 3.2 and the communication unit 10 to 10 reduce bandwidth. Rather, each workplace computer 3.1, 3.2 independently of any other workplace computer 3.2, 3.1 and also independently of the communication unit 10 reduces the bandwidth required to transmit image signals from the connected cameras 2.1, 2.2, 2.3 to the control centers Z, T. If a workplace computer 3.1, 3.2 has detected a low bandwidth, it regulates 15 each connected camera 2.1, 2.2, 2.3 downward as just described with the goal of reducing the respective required bandwidth. Here, the workplace computer 3.1, 3.2 causes a value of at least one bandwidth-relevant parameter that influences the bandwidth of a connected camera 2.1, 2.2, 2.3 to be changed with the goal of reducing the required bandwidth. Preferably, the workplace 3.1, 20   3.2 checks at least once what bandwidth is available after this reduction. If there is still not enough bandwidth available, the workplace computer 3.1, 3.2 again down-regulates at least one connected camera 2.1, 2.2, 2.3 with the objective of reducing the bandwidth. Preferably, the workplace computer 3.1, 3.2 later again regulates the camera 2.1, 2.2, 2.3 in the other direction, i.e. changes at least 25 one parameter value with the goal of again achieving a higher image quality through a higher resolution and / or higher frame rate and / or lower compression, even if this requires a higher bandwidth. In this way, each workplace 3.1, 3.2 automatically performs continuous closed-loop control of the bandwidth actually required to transmit the image signals from the connected 30 cameras 2.1, 2.2, 2.3. 2023345418   13 Jul 2026 According to the embodiment just described, each workplace computer 3.1, 3.2 causes the value of at least one parameter of the or at least one, preferably each, connected camera 2.1, 2.2, 2.3 to be changed with the objective of reducing or also increasing the bandwidth, which bandwidth is required to 5 transmit the image signals of all connected cameras 2.1, 2.2, 2.3. In one embodiment, the workplace computer 3.1, 3.2 changes the parameter value by a specified or also randomly selected absolute or percentage value. In another embodiment, the workplace computer 3.1, 3.2 determines how many persons are currently in or at the monitored workplace A.1, A.2 according to the 10 signals of the access control unit 6.1, 6.2. The workplace computer 3.1, 3.2 changes the parameter value with the following control objective: the greater the number of persons detected in or at the workplace A.1, A.2 is, the greater is the bandwidth available for the transmission of cameras 2.1, 2.2, 2.3 in or at this workplace A.1, A.2. One reason: the more people are currently there, the more 15 important it is that the operator in a control center Z, T detects an undesired event quickly and reliably. If, according to the access control unit 6.1, 6.2, there is nobody at all in or at the workplace A.1, A.2, the workplace computer 3.1, 3.2 causes a relatively low bandwidth. As already explained, however, even in this case at least one image signal is transmitted from this workplace A.1, A.2 to the 20 control centers Z, T - among other things because a person may be there who has not logged in. In one embodiment, the monitoring system comprises an image evaluation unit. This image evaluation unit is able to automatically evaluate the image signal of at least one camera 2.1, 2.2, 2.3 and to decide by means of the image 25 evaluation whether the image signal currently depicts a movement or not. As a rule, this movement originates from a worker at the monitored workplace A.1, A.2, but it can also originate from a falling object or an object that has moved in some other way. According to the embodiment with the image evaluation unit, the bandwidth required for transmitting the image signal from a camera 2.1, 2.2, 30   2.3 is then reduced if this image signal does not show any movement. 2023345418   13 Jul 2026 As explained above, the bandwidth required to transmit the image signal from a camera 2.1, 2.2, 2.3 to the central output computer 20 and to the tablet Tb is reduced. Preferably, the workplace computer 3.1, 3.2 to which said camera 2.1, 2.2, 2.3 is associated causes the required bandwidth to be reduced. As 5 explained above, at least one bandwidth-relevant parameter of the camera 2.1, 2.2, 2.3 is changed to reduce the bandwidth. Reducing the required bandwidth often also results in reduced image quality when displaying the image signal. In a preferred embodiment, the image quality is therefore increased again on a trial basis, even if more bandwidth is required to transmit the image signal after 10 the increase. To increase the image quality, at least one bandwidth-relevant parameter of the camera 2.1, 2.2, 2.3 is changed accordingly. Preferably, the workplace 3.1, 3.2 also triggers this increase of the image quality automatically. In one implementation, the step of increasing the image quality again is triggered at least when a specified time period has elapsed since a reduction of 15 the bandwidth. Furthermore, it is possible that the image quality is enlarged on a trial basis even if the required bandwidth has not been reduced beforehand. In one implementation, a workplace computer 3.1, 3.2 randomly enlarges image quality at random time points. For example, each workplace computer 3.1, 3.2 includes a respective random number generator that generates random time 20 points. Or, each workplace computer 3.1, 3.2 randomly enlarges image quality at a specified frequency, with each workplace computer 3.1, 3.2 applying a different frequency. Both configurations reduce the risk that several workplaces 3.1, 3.2 simultaneously enlarge the image quality on a trial basis, whereupon the available bandwidth is insufficient and then the bandwidth must be reduced 25 again, which can lead to instability. Preferably, the workplace computer 3.1, 3.2 determines whether sufficient bandwidth is available before an increase and / or after an increase of the image quality. If sufficient bandwidth is actually available, the increased image quality is retained. The camera 2.1, 2.2, 2.3 retains the corresponding values for 30 their bandwidth-relevant parameters. Otherwise, each bandwidth-relevant parameter is reassigned the old value, i.e. the value before the increase. 2023345418   13 Jul 2026 Preferably, for each camera 2.1, 2.2, 2.3 and for each bandwidth-relevant parameter of this camera 2.1, 2.2, 2.3, a respective value range is given. The parameter is only changed within this value range. Power supply for the workplace computer 5 As already explained, in one embodiment the workplace computer 3.1, 3.2 supplies electrical power not only to the internal electrical consumers, but also to the or each camera 2.1, 2.2, 2.3 and / or the or each gas measuring device 1.1, 1.2, 1.3, 1.4. It is also possible that at least one camera 2.1, 2.2, 2.3 and / or gas measuring device 1.1, 1.2, 1.3, 1.4 comprises its own voltage supply 10 unit. In a preferred embodiment, the workplace computer 3.1, 3.2 can be connected to a stationary voltage supply network and comprises, for example, a corresponding cable with a corresponding plug. However, it is often not possible to supply a workplace A.1, A.2 to be monitored with electrical energy through a 15 suitable stationary voltage supply network. In particular, it is often not possible or at least not desirable to install long power cables. In one embodiment, the communication unit 10 supplies the or at least one workplace computer 3.1, 3.2 with electrical power, preferably via a cable. The above-mentioned series connection between the communication unit 10 and at 20 least two workplace computers 3.1, 3.2 also allows the power supply for the connected workplace computers 3.1, 3.2 to be implemented: The communication unit 10 has its own voltage supply unit or is connected to a stationary power supply network. The communication unit 10 supplies the first workplace computer 3.1 with electrical power, preferably via a cable. The first 25 workplace computer 3.1 supplies electrical energy to the second workplace computer 3.2. It is also possible that the first workplace computer 3.1 permanently supplies the second workplace computer 3.2 with electrical energy, i.e. without the first workplace computer 3.1 being supplied with electrical energy by the communication unit 10. Preferably, each workplace computer 3.1, 30   3.2 nevertheless has its own voltage supply unit, which is used in the event that 2023345418   13 Jul 2026 the power supply by the communication unit 10 is interrupted or not possible due to local conditions. For the above reasons, the monitoring unit 100.1, 100.2 preferably has its own voltage supply unit which supplies at least the workplace computer 3.1, 3.2 with 5 electrical power, optionally additionally the or a camera and / or the or a gas measuring device 1.1, 1.2, 1.3, 1.4. Preferably, this voltage supply unit comprises at least one rechargeable battery (accumulator), preferably several batteries. A preferred embodiment of this dedicated voltage supply unit is described 10 below. The preferred embodiment satisfies the following limiting constraints: - In a potentially explosive environment, a device with an electrical component must not be unscrewed. - A voltage supply unit should not be charged in a potentially explosive 15 environment. In particular, a charger is often not implemented as an intrinsically safe device. - The monitoring of the workplace A.1, A.2 must not be interrupted as long as there is at least one worker there, not even to replace a voltage supply unit of the monitoring unit 100.1, 100.2. 20   - A device with its own voltage supply unit may only be transported by air freight if the voltage supply unit has a maximum of 100 Wh of electrical charge. According to the preferred embodiment, the voltage supply unit for the monitoring unit 100.1, 100.2 comprises an internal voltage source and at least 25 one external voltage source, preferably two external voltage sources. The internal voltage source is arranged in that housing which also accommodates the workplace computer 3.1, 3.2. Thus, the housing protects the internal voltage source to a certain extent from external damage. Figure 4 schematically shows the workplace computer 3.1 of the monitoring unit 30   100.1 for the workplace A.1. The workplace computer 3.1 comprises 2023345418   13 Jul 2026 - a housing 30, - an electrical consumer in the form of a circuit board 34, - an internal voltage source 31, and - two external voltage sources 32.1, 32.1' and 32.2, 32.2'. 5 The three voltage sources 31, 32.1, 32.2 together form the voltage supply unit for the workplace computer 3.1, optionally for the entire monitoring unit 100.1. In one embodiment, the workplace computer 3.1 is also capable of supplying electrical power to the camera 2.1 and the gas measuring devices 1.1, 1.2. The workplace computer 3.2 and the communication unit 10 can each comprise their 10 own voltage supply unit, which in one embodiment is constructed in the same way as that of the workplace computer 3.1. In the implementation shown as an example in Figure 4, the camera 2.1 is mechanically connected to the workplace computer 3.1 in a detachable manner, preferably via a coupling point at the top of the housing 30. The lens 9 and the 15 light source 11 of the camera 2.1 are shown as an example. The or each external voltage source 32.1, 32.1', 32.2, 32.2' can be detachably connected to the workplace computer 3.1. The workplace computer 3.1 is capable of determining the respective current level of each connected external voltage source 32.1, 32.1', 32.2, 32.2' and comparing it with at least one 20 specified lower level threshold. For example, a first level threshold is 3% or 5% and a second level threshold is 10% of the maximum level. Generally, the first level threshold is less than or equal to the second level threshold. Preferably, the detachable electrical connection between the workplace 3.1 and the external voltage source 32.1, 32.1', 32.2, 32.2' is established in one of the 25 following two ways: - In one embodiment, at least one coupling point for an external voltage source 32.1', 32.2' is embedded in the housing 30 of the workplace computer 3.1, preferably two coupling points for one external voltage source each. Because the workplace computer 3.1 is intrinsically safe, 30         an external voltage source 32.1', 32.2' may be connected to the coupling 2023345418   13 Jul 2026 point and disconnected from the coupling point again during operation, even if the workplace computer 3.1, 3.2 is located in a potentially explosive environment. - In another embodiment, a trough-shaped receptacle for an external 5         voltage source 32.1, 32.2 is recessed in the housing 30, wherein the receptacle comprises the required electrical contact points for the voltage source and a closure can optionally release or close the receptacle. Because the workplace computer 3.1 is intrinsically safe, the lock may be opened during operation, an external voltage source 32.1, 32.2 may be 10         removed from the receptacle, a new external voltage source 32.1, 32.2 may be inserted and the lock may be closed again. In the example of Figure 4, two receptacles for two external voltage sources 32.1 and 32.2 are recessed in the housing 30. An external voltage source 32.1, 32.2 can be inserted into one of these receptacles and removed from the 15 receptacle again. The two receptacles can each be closed with a closure 33.1, 33.2. Figure 4 also shows two coupling points 35.1, 35.2, to each of which an external voltage source 32.1', 32.2' can be connected, for example with a suitable plug. First, the embodiment with a single external voltage source 32.1 is described. 20 The workplace computer 3.1 is supplied with electrical energy from the external voltage source 32.1 until the level of the external voltage source 32.1 falls below the specified first level threshold. If the level has fallen below the first level threshold, the workplace computer 3.1 - more precisely: a signal-processing control unit for the workplace computer 3.1 which is not shown - switches the 25 voltage supply unit in such a way that the workplace computer 3.1 is now supplied by the internal voltage source 31. In addition, the workplace computer 3.1 generates a low level message. Preferably, the workplace computer 3.1 generates this low level message when the measured level has fallen below the second level threshold but is still above 30 the first level threshold. This message is preferably transmitted to the control centers Z, T and output in the control centers Z, T or any other spatially remote 2023345418   13 Jul 2026 receiver in a form perceptible by a human being. Preferably, this message is also output on a screen of the workplace computer 3.1. Later, the workplace computer 3.1 automatically detects the event that a new external power source 32.1 is connected to the workplace computer 3.1. Thereupon, the workplace 5 computer 3.1 switches back to a supply from the connected external voltage source 32.1. For the process of replacing the used external voltage source 32.1 with a new external voltage source 32.1, the time period is available which elapses until the level of the internal voltage source 31 has also fallen below a predefined level threshold. 10 The embodiment with a first external voltage source 32.1 and a second external voltage source 32.2 is described in the following. As long as the workplace computer 3.1 is simultaneously connected to two external voltage sources 32.1, 32.2, it is initially supplied with electrical energy from the first external voltage source 32.1 until the level of the first external voltage source 32.1 has fallen 15 below the specified first level threshold. Then the workplace computer 3.1 automatically switches to a supply from the second external voltage source 32.2. In addition, the workplace computer 3.1 again generates a message concerning the low level of the first external voltage source 32.1, preferably if its level has fallen below the second level threshold. The workplace computer 3.1 20 is supplied from the second external voltage source 32.2 until the level of the second external voltage source 32.2 has fallen below the first level threshold. As soon as the level of the second external voltage source 32.2 has fallen below the first level threshold, the system switches back to a supply from the first external voltage source 32.1 - provided that the used first external voltage 25 source 32.1 was replaced by a new external voltage source while the workplace computer 3.1 was supplied from the second external voltage source 32.2. Otherwise, the internal voltage source 31 is used. It is possible that the workplace computer 3.1 is always supplied from an external voltage source 32.1, 32.2 until its level has fallen below the first level 30 threshold. It is also possible that the workplace computer 3.1 is preferably supplied from the first external voltage source 32.1, namely as long as its level is above the first level threshold. The entire period during which the level of the 2023345418   13 Jul 2026 second external voltage source 32.2 is above the first level threshold is available for replacing the first external voltage source 32.1. At any given time, the workplace computer 3.1 is thus supplied with electrical energy from exactly one external voltage source 32.1 or 32.2, provided that the 5 level of this external voltage source 32.1, 32.2 is above the first level threshold. The internal voltage source 31 acts as a buffer storage which supplies the workplace computer 3.1 with electrical energy if and only if no connected external voltage source 32.1, 32.2 has a level above the first level threshold. It is possible to remove the workplace computer 3.1 from the potentially 10 explosive environment after use and to charge or replace the internal voltage source 31 outside the potentially explosive environment. As explained above, the communication unit 10 on the one hand forwards signals from the or each connected workplace computer 3.1, 3.2 to the control centers Z, T and conversely forwards messages from the control centers Z, T to 15 the or each connected workplace computer 3.1, 3.2. In one embodiment, the communication unit 10 can be connected to a stationary power supply network. Preferably, the communication unit 10 also has its own voltage supply unit. Particularly preferably, this voltage supply unit for the communication unit is configured in the same way as described above with reference to Figure 4 for 20 the workplace computer 3.1 with the internal voltage source 31 and the two external voltage sources 32.1, 32.2. Configuration of the control center as a transportable arrangement Figure 5, Figure 6, and Figure 7 show an example of an embodiment that makes it possible to quickly transport the devices of the first control center Z to 25 a desired location. On the one hand, this embodiment makes it possible to establish a directional radio link between the communication unit 10 and the central output computer 20. On the other hand, it is facilitated to set up the first control center Z at a location where a good connection with a public mobile radio network I, 15 can be achieved. 2023345418   13 Jul 2026 In order to transport the devices of the first control center Z, a two-part and preferably rigid housing 40 with a detachable housing part 40.1 and a support 40.2 is used. If the two housing parts 40.1, 40.2 are mechanically connected to each other, they enclose a space which is cuboidal in the embodiment example. 5 The detachable housing part 40.1 can be detachably connected to the support 40.2 by means of a plurality of snap locks 42.1, 42.2, ... on the detachable housing part 40.1 and corresponding projections 42.3, 42.4 on the support 40.2. The closed housing 40 can be placed on a trolley 41 and thereby be moved with relatively little effort. By means of snap locks 43.1, 43.2, the housing 40 can be 10 releasably connected to the trolley 41. The housing 40 preferably comprises handles 44.1, 44.2 on the detachable housing part 40.1 for transporting the housing 40. Figure 5 shows the housing 40 with the detachable housing part 40.1 connected to the support 40.2. In Figure 5 on the left, the trolley 41 is shown in front of the housing 40. In Figure 5 right, the housing 40 is shown on 15 the trolley 41. Figure 6 shows the three screens 22, 23.1, 23.2 on the support 40.2 after the detachable housing part 40.1 has been removed. The further screen 23.1 stands on a stand 45.1, the further screen 23.2 on a stand 45.2. The screen surfaces of the further screens 23.1, 23.2 face away from the viewer and 20 towards the screen surface of the overhanging overview screen 22. A transport carrier 46 is detachably or fixedly connected to the support 40.2 and supports the further screens 23.1, 23.2 during transport. The two additional screens 23.1, 23.2 can be lifted from the support 40.2 and positioned to the left or right of the overview screen 22. In one embodiment, the 25 overview screen 22 is mechanically connected to the support 40.2 so that the support 40.2 also functions as a stand for the overview screen 22. During transport, the housing 40 preferably further accommodates the central output computer 20, the headphones 21 with the microphone 27, and the communication unit 47. In one embodiment, the devices of the first control 30 center Z are connected to each other in advance by cables and are brought onto the support 40.2 in the wired state. The detachable housing part 40.1 is 2023345418   13 Jul 2026 placed on the support 40.2 and connected to the support 40.2 to form a housing 40 as shown in Figure 5. The housing 40 encloses the wired devices of the first control center Z. At a location of use, the detachable housing part 40.1 is removed from the support 40.2. The two other screens 23.1, 23.2 are positioned 5 adjacent to the overview screen 22, a connection is made to a stationary power supply network or a dedicated voltage supply unit, and the communication unit 47 is connected to the Internet and in particular to the central computer 15. In many cases, only a few minutes are required to set up the first control center Z. Structure and function of the control center 10 As already explained, an operator in a control center Z, T monitors the workplace A.1, A.2. The control center Z comprises a central output computer 20. The central output computer 20 and the tablet Tb can be connected to a stationary power supply network. In one embodiment, the central output computer 20 and the tablet Tb each additionally comprise or can be connected 15 to a dedicated voltage supply unit. The dedicated voltage supply unit allows the central output computer 20 and the tablet Tb to be positioned close to the or a workplace to be monitored, even if no stationary power supply network is available there. The dedicated voltage supply unit can be configured as described above for the workplace computer 3.1 with reference to Figure 4. 20 The first control center Z of the embodiment comprises an overview screen 22 and optionally at least one further screen 23.1, 23.2. Preferably, the overview screen 22 is larger than the or each further screen 23.1, 23.2. For example, the overview screen 22 has a diagonal of 43 inches, and the or each further screen 23.1, 23.2 has one of 24 inches. In one embodiment, two further screens 23.1, 25   23.2 are laterally and rotatably attached to the overview screen 22, similar to two wings of an altarpiece (retable) known from a church. It is also possible that the or each further screen 23.1, 23.2 is set up next to the overview screen 22, in particular with the aid of a respective stand 45.1, 45.2. It is possible that the operator in a control center Z, T simultaneously monitors several 30 workplaces A.1, A.2. In this embodiment, the overview screen 22 or the screen of the tablet Tb is divided into several areas (windows) 24.1, 24.2. On each area 2023345418   13 Jul 2026 24.1, 24.2, image signals from a respective camera 2.1, 2.2, 2.3 are displayed. The operator can select a displayed area 24.1, 24.2 and thereby a monitored workplace A.1, A.2. On a further screen 23.1, 23.2 the image signals as well as measured values and further information from the selected monitored workplace 5   A.1 are displayed. In particular, one respective signal from each gas measuring device 1.1, 1.2 installed at the workplace A.1 is displayed there. In one embodiment, the operator may control the or each camera 2.1, 2.2, 2.3 at a monitored workplace A.1, A.2 from the control center Z, T. In particular, the operator may cause one of the following changes to be performed on the 10 camera 2.1, 2.2, 2.3: - An optional actuator swivels and / or shifts the camera 2.1, 2.2, 2.3 and in particular changes the viewing direction and / or the viewing angle and / or the imaging scale of the camera 2.1, 2.2, 2.3. - The focal length and thus the mapping scale of the camera 2.1, 2.2, 2.3 are 15 changed. The camera 2.1, 2.2, 2.3 thus zooms into or out of the workplace. - An optional light source of the camera 2.1, 2.2, 2.3 is switched on or off. - The camera 2.1, 2.2, 2.3 is switched on or off. - The resolution and / or the frame rate with which the photosensor of the camera 2.1, 2.2, 2.3 generates images is changed. This changes the 20 bandwidth required to transmit the image signal of the camera 2.1, 2.2, 2.3. - Changed is a bandwidth-relevant parameter of an algorithm which the image processing unit of the camera 2.1, 2.2, 2.3 applies to process the images of the photosensor and to generate the image signal of the camera 2.1, 2.2, 2.3 by the processing. 25 The operator is informed visually and / or acoustically that one of several possible alarm situations has occurred. Or the operator himself or herself detects an alarm situation. Examples of alarm situations are: - A gas measuring device 1.1, 1.2, 1.3, 1.4 has detected a target gas concentration above a specified concentration threshold. 30   - The optional image evaluation unit has automatically detected a hazardous situation at the monitored workplace A.1, A.2, for example a fire or a very 2023345418   13 Jul 2026 rapid movement. Such a movement can be caused by a falling object or a fall of a worker. - A workplace computer 3.1, 3.2 for a monitored workplace A.1, A.2 has detected that it is not receiving an image signal from a camera and / or a 5 signal from a gas measuring device 1.1, 1.2, 1.3, 1.4 and / or from a voice input unit 4.1, 4.2 and / or from an access control unit 6.1, 6.2. - The communication unit 10 has detected that it is not receiving a signal from a workplace computer 3.1, 3.2. - The operator has discovered that a screen 22, 23.1, 23.2 in the control 10 center Z, T shows a dangerous situation at a monitored workplace A.1, A.2, for example, an accident or a fire. - The data connection between a monitoring unit 100.1, 100.2 and a control center Z, T is interrupted. - A worker has signaled that an alarm is to be triggered at workplace A.1, A.2. 15   - The operator has discovered that a worker at workplace A.1, A.2 is not wearing the prescribed protective equipment and / or has not registered with the access control unit 6.1, 6.2. The first event can often be detected in images from at least one camera 2.1, 2.2, 2.3. The second event can lead to the fact that in an image of the workplace A.1, A.2 more persons can be 20 seen than are - according to the access control unit 6.1, 6.2 - currently in or at the workplace A.1, A.2. As shown above, in one embodiment, the overview screen 22 is divided into a plurality of areas 24.1, 24.2, with image signals from a camera 2.1, 2.2, 2.3 being displayed on each area 24.1, 24.2, respectively. If a gas measuring 25 device 1.1, 1.2, 1.3, 1.4 detects an alarm at a workplace A.1, A.2, each area on the overview screen 22 on which an image signal from this workplace A.1, A.2 is displayed is highlighted. Thus, the alarm is visually output. For example, a frame 27.1, 27.2 around the area 24.1, 24.2 is displayed differently. In addition, an alarm is preferably output acoustically, for example by an acoustic signal on 30 the operator's headphones 21. Figure 3 shows a schematic example of how an alarm situation is presented to the operator in the control center Z: 2023345418   13 Jul 2026 - The frame 27.1 around window 24.1 is highlighted. This indicates that an alarm situation has occurred at the workplace A.1. - An acoustic message is output on the headphones 21. - On the further screen 23.1 two windows 25 and 26 are shown. 5   - Measured target gas concentrations con.1, con.2, which the two gas measuring devices 1.1 and 1.2 measured at workplace A.1, are shown in the window 26. The target gas concentration con.1 is highlighted. This indicates in a visually perceptible way that this value is above a concentration threshold and therefore dangerously high. Based on this measurement, the 10 gas measuring device 1.1 has triggered the alarm for workplace A.1. The operator selects the or each workplace A.1 that is affected by the alarm situation. For example, a harmful gas has leaked or a fire has broken out at a workplace A.1. Then workplaces above and / or next to it are also affected. The operator effects for the or each selected workplace A.1 the step that an 15 alarm is triggered at this workplace A.1. Triggering an alarm causes the following actions, either automatically or after a corresponding confirmation by the operator: - The alerting element 7.1, 7.2 issues an alarm visually and acoustically. A required consequence is that workplace A.1 is evacuated. 20   - The access control unit 6.1 notifies a worker who wants to log in that the workplace A.1 is locked and must not be entered. - A message comprising the alarm is transmitted to at least one other communication unit, for example, to a communication unit of a plant fire department or an ambulance station. 25 In the event of an alarm, a notification window is also opened on one screen, preferably on another screen 23.1, 23.2. The operator can cause the actions with which he or she reacts to the alarm by making entries in this notification window. The notification window shows possible actions to be taken by the operator in response to an alarm in many cases, but not in every case. 30 Examples are: 2023345418   13 Jul 2026 - Workplace A.1 is locked as just described above. - A paramedic is notified and told to go to the work site. Figure 3 illustrates this by way of example: A list is shown in the window 25. This list shows actions to be taken after the occurrence of an alarm at 5 workplace A.1. Three actions A, B, C are shown as an example. Next to each action of the list in window 25 an input field is shown. In one implementation, the operator makes an entry in an input field next to an action A, B, C, thereby triggering that action A, B, C. In another implementation, the operator triggers the action A, B, C and then confirms that he or she has triggered this action A, 10 B, C by making an entry in the input window. In both implementations, it is the operator's responsibility which actions he or she actually triggers. The list in the window 25 reduces the risk that the operator does not trigger a required action A, B, C. On the other hand, a corresponding action A, B, C is only triggered after the operator has released it. 15 The operator in a control center Z, T is also informed of events that also require a response, but do not require work at a workplace A.1, A.2 to be interrupted immediately. Examples of such events are: - In order to transmit image signals from the workplace A.1, A.2 to a control center Z, T, only little bandwidth is available. One possible reaction, namely 20 a down-regulation of the or a camera 2.1, 2.2, 2.3 at this workplace A.1, A.2, has already been described above. As already explained, this reaction is triggered automatically. The operator can also trigger this action. - The level of an external voltage source 32.1, 32.2 for a device of a monitoring unit 100.1, 100.2 has fallen below the specified second level 25 threshold. The voltage source 32.1, 32.2 must be replaced. Preferably, it is ensured that the operator actually monitors each workplace A.1, A.2. Of course, it can never be ruled out that an operator suffers a fainting spell or an accident and therefore can no longer perform the monitoring. Preferably, therefore, the central output computer 20 and the tablet Tb check how much 30 time has elapsed since the last user input at the control center Z, T. If the elapsed time is greater than a specified first time duration threshold, the central 2023345418   13 Jul 2026 output computer 20 and the tablet Tb preferably cause a request to be issued to the operator to now perform a user input. If no user input is detected after a further time period of a specified duration has elapsed, the central output computer 20 and the tablet Tb each generate a corresponding alert message 5 and cause that alert message to be transmitted to a spatially remote receiver. This receiver is, for example, a computer of another operator ("field operator"). In one embodiment, a data connection can be established between this computer, which acts as the receiver of the alarm message, and the central computer 15, so that the further operator can also monitor the or each 10 workplace A.1, A.2 remotely. In addition, the central output computer 20 preferably causes an alarm to be output at each workplace A.1, A.2. 2023345418   13 Jul 2026 List of reference signs 1.1, 1.2 Gas measuring device of the workplace A.1 1.2 Gas measuring device, attached to the outside of the workplace A.1, connected to the hose 8 1.3 Gas measuring device in workplace A.2 1.4 Gas measuring device in front of inlet E.2 to workplace A.2 2.1 Camera in workplace A.1 2.2, 2.3 Cameras in the workplace A.2 3.1 Workplace computer of the monitoring unit 100.1, carries the camera 2.1 3.2 Workplace computer of the monitoring unit 100.2 4.1 Voice input unit in the workplace A.1 4.2 Voice input unit in the workplace A.2 5.1 Voice output unit in the workplace A.1 5.2 Voice output unit in the workplace A.2 6.1 Access control unit in the workplace A.1 6.2 Access control unit in the workplace A.2 7.1 Alarm input element in workplace A.1 7.2 Alarm input element in workplace A.2 8 Hose through which the gas measuring device 1.2 can suck in a gas sample from the workplace A.1 9 Camera lens 2.1 10 Communication unit (router), which establishes a connection between the workplace computers 3.1 and 3.2 on the one hand and the control centers Z, T on the other hand 2023345418   13 Jul 2026 11 Camera light source 2.1 13.1, 13.2 Temperature sensor at the workplace A.1, A.2 15 Central computer, comprises the monitoring system area 16, is in a respective bidirectional data connection with the communication unit 10 and the control centers Z, T via the mobile radio network. 16 Monitoring system area on the central computer 15, is used for the monitoring system 17 Processing of the signals from the monitoring units 100.1, 100.2, is generated by the processing program 18 18 Processing program, which belongs to the monitoring system area 16, preferably realized as a web server 20 Central output computer of the first control center Z, connected to each workplace computer 3.1, 3.2 via the communication unit 10, capable of controlling the screens 22, 23.1 and 23.2 and the headphones 21 and receiving a voice input from the microphone 27, capable of receiving data from the central computer 15 21 Headphones in the control centers Z, T 22 Overview screen of the first control center Z, displays one image signal from each camera 2.1,2.2, 2.3 23.1 A further screen of the first control center Z, hingedly connected to the overview screen 22, displays in window 25 the measures to be taken after an alarm and in window 26 the measured target gas concentrations con.1, con.2 23.2 A further screen of the first control center Z, hinged to the overview screen 22, displays windows 25 and 26 2023345418   13 Jul 2026 24.1 Window for display A.1' of the image signal from the camera 2.1 on the overview screen 22 and the screen 28, shows the monitored workplace A.1 24.2 Window for displaying A.2' of the image signal from camera 2.2 on the overview screen 22 and the screen 28, shows the monitored workplace A.2 25 Window on the further screen 23.1 list the actions A, B, C to be taken after the alarm at the workplace A.1 26 Window on the further screen 23.1, in which the target gas concentrations con.1, con.2 measured at the workplace A.1 are displayed 27 Microphone in the control centers Z, T, connected to the headphones 21 28 Tablet screen Tb 30 Housing of the workplace computer 3.1 31 Internal voltage source of the workplace computer 3.1 32.1 First external voltage source, can be detachably inserted into a troughshaped receptacle and thus connected to the workplace computer 3.1 32.1' First external voltage source, can be detachably connected to a coupling point 35.1, 35.2 32.2 Second external voltage source, can be detachably inserted into a troughshaped receptacle and thus connected to the workplace computer 3.1 32.2' Second external voltage source, can be detachably connected to a coupling point 35.1, 35.2 2023345418   13 Jul 2026 33.1, 33.2 Closure for a receptacle in which an external voltage source 32.1, 32.2 can be inserted and removed again 34 Circuit board of the workplace computer 3.1 35.1, 35.2 Coupling points in housing 30 for one external voltage source each 32.1', 32.2' 40 Housing for the devices of the first control center Z, comprises a detachable housing part 40.1 and a support 40.2, can be placed on the trolley 41 40.1 Detachable housing part of the housing 40, can be detachably connected to the support 40.2, the snap locks 43.1, 43.2, the handles 44.1,44.2, 44.3 40.2 Support of the housing 40, has the projections 42.3, 42.4, preferably functions as a stand for the overview screen 22 41 Trolley for transporting the housing 40 42.1, 42.2 Snap fasteners on the detachable housing part 40.1 for detachable connection of the detachable housing part 40.1 to the support 40.2 42.3, 42.4 Projections on the support 40.2 for detachably connecting the detachable housing part 40.1 to the support 40.2 43.1, 43.2 Snap locks for detachably connecting the housing 40 to the trolley 41 44.1, 44.2 Handles on detachable housing part 40.1 45.1, 45.2 Stand for the further screen 23.1,23.2 46 T ransport carrier for screens 22, 23.1, 23.2 2023345418   13 Jul 2026 47 Communication unit (router) of the control center Z 48 Output program on the central output computer 20 49 Output program on the tablet TB 50 Mouse of the central output computer 20 100.1 Workplace monitoring unit A.1, includes gas measuring devices 1.1 and 1.2, camera 2.1, workplace computer 3.1, voice input unit 4.1, voice output unit 5.1, alarm input element 7.1, and hose 8 100.2 Workplace monitoring unit A.2, includes gas measuring devices 1.3 and 1.4, cameras 2.2 and 2.3, workplace computer 3.2, voice input unit 4.2, voice output unit 5.2, and alarm input element 7.2 A.1 Workplace monitored by means of the monitoring unit 100.1 includes the input E.1 A.1' Display from workplace A.1 on an output unit 22, 28 of the control center Z, T A.2 Workplace monitored by means of the monitoring unit 100.2 includes input E.2 A.2' Display from workplace A.2 on an output unit 22, 28 of the control center Z, T con.1, con.2 Target gas concentrations at the workplace A.1, measured by the gas measuring device 1.1, displayed on the further screen 23.1 E.1, E.2 Entrance to the workplace A.1, A.2 I Internet through which the communication unit 10 is connected to the control centers Z and T T Further control center, realized on the tablet Tb, includes the screen 28, the headphone 21 and the microphone 27 Tb Tablet of the further control center T, includes the screen 28 2023345418   13 Jul 2026 Z First control center, includes the central output computer 20, headphones 21, mouse 50, overview screen 22, other screens 23.1, 23.2, microphone 27, and communication unit 47

Claims

1. A monitoring system for monitoring at least one workplace,wherein the monitoring system comprises for the or each monitored workplace a respective monitoring unit,5 wherein the monitoring system further comprises- a communication unit and- a first control center,wherein the first control center- is physically remote from the communication unit and the or each10          monitoring unit, and- comprises a central output computer and an output unit,wherein the or each monitoring unit respectively includes- at least one camera,- at least one gas measuring device, and15      - a workplace computer,wherein the or each camera is configured to generate a respective image signal from the monitored workplace,wherein the or each gas measuring device is configured to measure an indicator for the respective concentration of at least one target gas at the20 monitored workplace,wherein in a first alternative the or each gas measuring device and in a second alternative the workplace computer of the respective monitoring unit of a monitored workplace are configured to- compare a measured target gas concentration with a specified range of25          concentration values or with a concentration threshold, and,- if the measured target gas concentration is outside the specified range or above the concentration threshold, to generate an alarm,2023345418   13 Jul 2026wherein the or each camera and the or each gas measuring device of a monitoring unit are connected or connectable to the workplace computer of this monitoring unit by cable and / or wirelessly, or by radio waves,wherein the or each workplace computer is connected or connectable to the 5 communication unit by a respective data connection by cable and / orwirelessly, or by radio waves,wherein the communication unit is connected or connectable to the central output computer by a data connection,wherein the data connection between the communication unit and the10 central output computer comprises a wireless data connection, or radio waves,wherein the data connection between the communication unit and the central output computer is completely or at least partially routed via a public mobile radio network,15 wherein the public mobile radio network uses a central computer,wherein an area of the central computer is permanently or at least temporarily in a data connection with the communication unit and permanently or at least temporarily in a data connection with the central output computer,20 wherein the monitoring system is configured to transmit every respective image signal of the or each camera and every alarm from the or each gas measuring device or workplace computer to the central output computer via the respective workplace computer and the communication unit, andwherein an output program is installed on the central output computer,25 wherein the central output computer is configured to control, using the output program, the output unit in such a way that the controlled output unit outputs for each monitored workplace a respective representation,wherein the representation for a workplace shows2023345418   13 Jul 2026- in at least one form perceptible by a human, or visually, every alarm from the or each gas measuring device or workplace computer and- at any time during the monitoring the respective image signal of the or each camera of the respective workplace,5 wherein the area of the central computer comprises a processing program which is executable on the central computer,wherein the processing program is configured to generate presentation data upon execution of the processing program,wherein the presentation data comprises each alarm from the or each gas10 measuring device or workplace computer and the respective image signal from the or each camera representable in at least one form perceptible by a human, or visually, andwherein the central output computer is configured to control the output unitin such a way that the representation which the controlled output unit15 outputs represents the presentation data generated by the processing program.

2. The monitoring system according to claim 1,wherein20 the monitoring system comprises a first monitoring unit for a first monitored workplace and a second monitoring unit for a second monitored workplace,each of said two monitoring units respectively includes- at least one camera,- at least one gas measuring device and25      - a workplace computer,wherein the respective workplace computer of each of said two monitoring units is connected or connectable to the communication unit by a respective data connection, and / orthe communication unit is arranged outside each monitored workplace.2023345418   13 Jul 20263. The monitoring system according to claim 1 or claim 2,whereinthe monitoring system comprises at least one second control center,5 wherein the second control center- is physically remote from the first control center, the communication unit, and the or each monitoring unit, and- comprises a second central output computer and a second output unit,wherein the area of the central computer is permanently or at least 10 temporarily in a data connection with the second central output computer,wherein a second output program is installed on the second central output computer,wherein the second central output computer is configured to control the second output unit using the second output program such that a15 representation which the second output unit outputs, represents the presentation data generated by the processing program.

4. The monitoring system according to any one of the preceding claims, wherein20 the transmission of an image signal from the or each camera to the central output computer requires a bandwidth andthe or each camera has at least one bandwidth-relevant parameter, which affects the bandwidth required for transmitting the image signal,wherein the monitoring system is configured to automatically control the or 25 each camera with the objective that the respective value of the or at least one bandwidth-relevant parameter is changed in such a way that the bandwidth required for transmitting the image signal from the or each camera is changed.2023345418   13 Jul 20265. The monitoring system according to claim 4,whereinthe monitoring system is configured to automatically5      - determine an indicator for the bandwidth currently available for a datatransmission from the communication unit to the central output computer,or to detect an indication of insufficient bandwidth, and- depending on the determined available bandwidth, control the or each camera10         with the objective of changing the value of the or at least one bandwidthrelevant parameter of the or each respective cameraor with the objective of reducing the bandwidth required for transmission.

6. The monitoring system according to claim 5,15 whereinthe or each workplace computer of a monitoring unit is configured to automatically- determine the indicator for the currently available bandwidth and- depending on the determined bandwidth control the or each camera of20          this monitoring unit with the objective of changing the parameter value.

7. The monitoring system according to any one of claims 4 to 6,whereinat least one monitoring unit comprises an access control unit for the25 monitored workplace,2023345418   13 Jul 2026wherein the monitoring system is configured to determine, using signals from the access control unit, how many persons are currently in or at that workplace which is monitored by the monitoring unit,wherein the monitoring system, or the monitoring unit, is configured to5 control the or each camera of the respective workplace depending on the determined number of persons in or at the workplace,wherein the objective of the control is to change the value of the bandwidthrelevant parameter of the camera in such a way that- the smaller the determined number of persons, the smaller the required10         bandwidth, and- the controlled camera transmits an image signal even if the access control unit has not detected a person in or at the workplace.

8. The monitoring system according to any one of the preceding claims,15 whereinthe monitoring system is configuredif the or each gas measuring device or workplace computer has generated an alarm, to transmit to the first control center both the alarm and a message containing the target gas concentration resulting in the alarm,20 and / or wherein the monitoring system is configured to transmit the alarm with a higher priority than the target gas concentration message.

9. The monitoring system according to any one of the preceding claims,wherein25 the output unit comprises a screen,wherein the central output computer is configured to control the output unit in such a way that2023345418   13 Jul 2026the controlled output unit outputs for the or each monitored workplace the representation for each workplace in a respective area of the screen,wherein the representation, which is output in the screen area for a workplace, includes5      - the respective image signal from the or each camera at each workplaceas well as- a visually perceptible indication as to whether or not the or each gas measuring device or the workplace computer at the respective workplace has generated an alarm.1010. The monitoring system according to any one of the preceding claims,whereinthe monitoring system comprises a monitoring system housing,wherein the monitoring system housing15      - provides an enclosed space and- is configured to accommodate in the enclosed space at least the central output computer and the output unit of the first control center.

11. The monitoring system according to claim 10,20 wherein the monitoring system housing comprises a detachable housingpart and a support,wherein the detachable housing part can detachably be connected to the support,wherein the detachable housing part and the support, when joined together, 25 provide the enclosed space, andwherein the support- is connected to a component, or a screen, of the output unit, and- provides a stand for this component.2023345418   13 Jul 202612. The monitoring system according to any one of the preceding claims,whereinthe output unit of the first control center comprises an overview screen and5 at least one further screen,wherein the central output computer is configured to control the overview screen in such a manner that the controlled overview screen outputs the representation for the or each monitored workplace in a respective area of the overview screen for each workplace,10 wherein the central output computer is further configured to control the or each further screen in such a manner thatafter a selection of a monitored workplace or after receipt of an alarm from a workplacethe controlled further screen outputs the or each target gas concentration15 measured by the or each gas measuring device which is arranged at the respective workplace and which has generated the alarm.

13. The monitoring system according to any one of the preceding claims,wherein20 the central output computer is configured to control the output unit in such a way thatafter receiving an alarm from a gas measuring device or workplace computerthe controlled output unit outputs a list in a form perceptible by a human,25 wherein the output list- specifies the monitored workplace to which the alarm relates and- specifies at least one action to be performed as a consequence of this alarm at the respective monitored workplace.2023345418   13 Jul 202614. The monitoring system according to claim 13, whereinthe output unit of the first control center comprises an overview screen and5 at least one further screen,wherein the central output computer is configured to control the overview screen in such a mannerthat the controlled overview screen outputs the representation for the or each monitored workplace in a respective area of the overview screen for10 this workplace,wherein the central output computer is further configured to, upon receipt of an alarm,- control the overview screen in such a way that the overview screen outputs in the respective screen area the representation for the15         workplace at which the alarm was generated in a different manner thanthe representation for the or each further workplace from which no alarm originates and- control the or each further screen in such a way that the or each controlled further screen outputs the list.2015. The monitoring system according to any one of the preceding claims, whereinthe or each workplace computer- comprises a workplace computer housing and a respective voltage25         supply unit and- comprises at least one electrical consumer and / or is electrically connected or connectable to at least one electrical consumer,2023345418   13 Jul 2026or the or each electrical consumer is the or each camera and / or the or each gas measuring device,wherein each respective voltage supply unit comprises an internal voltage source and at least one external voltage source,5 wherein the internal voltage source is located inside the workplace computer housing,wherein the or each external voltage source is detachably connected or is capable of being detachably connected to the respective workplace computer,10 wherein the or each workplace computer is configured- to supply the or each electrical consumer with electrical energy from the or each connected external voltage source for as long as the level of the external voltage source is above a specified first level threshold, and- to generate a message when the level is below the first or below a15          second specified level threshold,wherein the second level threshold is equal to or greater than the first level threshold.

16. The monitoring system according to claim 15,20 whereinthe voltage supply unit comprises a first external voltage source and a second external voltage source,wherein the or each workplace computer is configured- if both external voltage sources are connected to the respective25         workplace computer at the same time,to supply the or each electrical consumer with electrical energy from the first external voltage source until the level of the first external voltage source is below the first level threshold, and2023345418   13 Jul 2026- subsequently to supply the or each electrical consumer from the second external voltage source.

17. The monitoring system according to claim 15 or claim 16,5 whereinthe or each workplace computer is configured,if the respective level of the or each connected external voltage source is below the first level threshold,to supply the or each electrical consumer, from the internal voltage source.1018. The monitoring system according to any one of the preceding claims, whereinthe monitoring system comprises a first monitoring unit and a second monitoring unit,15 wherein the two workplace computers of these two monitoring units and the communication unit are connected or connectable in series in such a way that- the workplace computer of the first monitoring unit is connected or connectable to the communication unit by a first data connection and20      - the workplace computer of the second monitoring unit is connected orconnectable to the workplace computer of the first monitoring unit by a second data connection.

19. The monitoring system according to any one of the preceding claims,25 whereinthe central output computer is configured to automatically2023345418   13 Jul 2026- check whether at least one respective message has arrived at the central output computer from the or each workplace computer within a specified time period,wherein the message is an alarm from the or each gas measuring device5         connected to each respective workplace computer or from this workplacecomputer and / or the image signal from the or each camera connected to each respective workplace computer and / or a message generated by each respective workplace computer, and- if no such message has been received from the or each workplace10         computer at the end of the time period, to generate and output a failurealarm on the output unit in a form perceptible by a human,wherein the failure alarm identifies the workplace to which the respective workplace computer is assigned.15   20. The monitoring system according to claim 19,whereinthe central output computer is configured to- generate a request message for the or each connected workplace computer at the beginning of each time period and20      - to cause the request message to be transmitted to each respectiveworkplace computer,the monitoring system is configured to transmit the or each request message to the associated workplace computer, andthe or each workplace computer is configured25      - to generate a response message in response to the receipt of a requestmessage, and- to cause the response message to be transmitted to the central output computer.2023345418   13 Jul 202621. The monitoring system according to any one of the preceding claims, whereinthe or each workplace computer is configured to automatically- check whether at least one message from the central output computer5         has arrived at the respective workplace computer within a specified timeperiod and- if no message has arrived at the respective workplace computer within the specified time period,generate a warning and output this warning at the monitored workplace 10         in a form that can be perceived by a human.

22. The monitoring system according to claim 21, whereinthe central output computer is configured15      - to generate a request message for the or each workplace computerwithin the time period and- to cause the request message to be transmitted to the assigned workplace computer.20   23. A monitoring process for monitoring at least one workplaceusing a monitoring system, the monitoring system comprising for the or each monitored workplace a respective monitoring unit,wherein the monitoring system further comprises- a communication unit and25       - a first control center,wherein the first control center2023345418   13 Jul 2026- is physically remote from the communication unit and the or each monitoring unit, and- comprises a central output computer and an output unit,wherein the or each monitoring unit respectively includes5      - at least one camera,- at least one gas measuring device, and- a workplace computer,wherein during the monitoring of the or each workplace the respective steps are performed that10 the or each camera generates a respective image signal of the monitored workplace,the or each gas measuring device measures an indicator for the respective concentration of at least one target gas at the monitored workplace,wherein in a first alternative the or each gas measuring device and in a15 second alternative the workplace computer of the respective monitoring unit of the monitored workplace- compares a measured target gas concentration with a specified range of concentration values or a concentration threshold and,- if the measured target gas concentration is outside the specified range or 20         above the concentration threshold, generates an alarm,the respective image signal of the or each camera and each alarm from the or each gas measuring device or workplace computer are transmitted from the monitored workplace via the workplace computer and the communication unit to the central output computer,25 the central output computer controls the output unit, andthe controlled output unit displays for each monitored workplace a respective representation,wherein the representation for a monitored workplace comprises, in at least one form perceptible by a human, every alarm from the or each gas2023345418   13 Jul 2026measuring device or workplace computer and the image signal from the or each camera of the respective monitored workplace,wherein the image signal of the or each camera is transmitted by means of a respective data connection by cable and / or wirelessly, or by radio waves, to5 the workplace computer of the respective monitoring unit,wherein in the first alternative the alarm from the gas measuring device or workplace computer is transmitted to the workplace computer, andwherein the image signal and the alarm- are transmitted from the workplace computer to the communication unit 10         by means of a data connection by cable and / or wirelessly, or by radiowaves, and- are transmitted from the communication unit to the central output computer,wherein the transmission from the communication unit to the central output 15 computer is carried out wirelessly, or by means of radio waves,wherein the data connection between the communication unit and the central output computer is completely or at least partially routed via a public mobile radio network,wherein the public mobile radio network uses a central computer,20 wherein an area of the central computer is permanently or at least temporarily in a data connection with the communication unit and permanently or at least temporarily in a data connection with the central output computer,wherein the area of the central computer comprises a processing program25 which is executable on the central computer,wherein an output program is installed on the central output computer,wherein, upon execution of the processing program, the processing program generates presentation data,2023345418   13 Jul 2026wherein the presentation data comprises for each monitored workplace every alarm from the or each gas measuring device or workplace computer and the respective image signal from the or each camera and is representable in at least one form perceptible by a human, or visually, and5 wherein the central output computer controls the output unit using the output program such that the representation which the controlled output unit outputs represents the presentation data generated by the processing program.10   24. The monitoring process according to claim 23,whereinthe or each camera has at least one bandwidth-relevant parameter, that is a parameter having a value that influences the bandwidth required to transmit the image signal from the or each respective camera and15 the monitoring process further comprising the automatically performed steps that- an indicator for the bandwidth which is currently available for data transmission from the communication unit to the central output computer is determined, and20       - if it is detected that the available bandwidth is too low,- at least one camera is controlled with the objective to change the value of a bandwidth-relevant parameter of the respective controlled camera andby this change to reduce the bandwidth required to transmit the image signal from the respective controlled camera,25         and / or the steps of determining the indicator for the bandwidth andcontrolling the camera are performed by the workplace computer of the respective workplace which is monitored by means of the respective controlled camera.2023345418   13 Jul 202625. The monitoring process according to claim 24,wherein the process further comprises- controlling the at least one camera with the objective of changing the value of a bandwidth-relevant parameter of the respective controlled5         camera and, by the change, increasing on a trial basis the image qualityof the image signal from the respective controlled camera ,- determining whether sufficient bandwidth is available to transmit the image signal with the increased image quality to the central output computer,10      - if sufficient bandwidth is available, retaining the changed parameter, and- if sufficient bandwidth is not available, controlling the at least one camera with the objective of changing the value of the bandwidth-relevant parameter or another bandwidth-relevant parameter of the respective controlled camera to reduce the required bandwidth again by the change,15 and / or these steps are performed by the workplace computer of the respective workplace which is monitored by means of the respectivecamera.

Images