Data output circuit, fire alarm terminal, and fire alarm system

Abstract

To prevent an abnormality due to ion migration from occurring while suppressing an increase of a cost of a substrate.SOLUTION: A data output circuit includes: a substrate; a first transmission line and a second transmission line; a bias voltage application section for applying a bias voltage; a first switch for performing switching between a connection state where the bias voltage application section is electrically connected to the first transmission line and the second transmission line and a disconnection state where not connected; a switch control section for performing switching on whether the bias voltage is to be applied to the first transmission line and the second transmission line; and a data output section for outputting transmission data based on electric signals respectively transmitted by the first transmission line and the second transmission line.SELECTED DRAWING: Figure 6

Description

Technical Field

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[0001] The present invention relates to a data output circuit, a fire alarm terminal, and a fire alarm system.

Background Art

[0002] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In a first embodiment of the present invention, a data output circuit is provided comprising: a substrate; a first transmission line and a second transmission line formed on the substrate having lands or vias and transmitting electrical signals when a bias voltage is applied; a bias voltage application unit for applying the bias voltage to the first transmission line and the second transmission line; a first switch for switching between a connected state and a disconnected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected; a switch control unit for controlling the first switch to switch whether or not to apply the bias voltage to the first transmission line and the second transmission line; and a data output unit connected to the first transmission line and the second transmission line and outputting transmission data based on the electrical signals transmitted by the first transmission line and the second transmission line, respectively, wherein the switch control unit connects the first switch when the data output unit acquires electrical signals from the first transmission line and the second transmission line in order to output the transmission data, and disconnects the first switch after the data output unit has acquired electrical signals from the first transmission line and the second transmission line.

[0007] A first resistor having a predetermined resistance value may be further provided between the first switch and the first transmission line, and between the first switch and the second transmission line.

[0008] The system further includes a second switch that switches between a connected state and a disconnected state where the reference potential and the first and second transmission lines are connected. The switch control unit may control the first and second switches to connect the first switch and apply the bias voltage to the first and second transmission lines, by disconnecting the second switch when the first switch is in the connected state, and connecting the first and second transmission lines to the reference potential when the first switch is in the disconnected state.

[0009] The first transmission line is further comprising a switch that switches between a connected state where it is electrically connected to a reference potential and a disconnected state where it is not connected, and maintains a state corresponding to a set value, and a switch that switches between a connected state where it is electrically connected to the reference potential and a disconnected state where it is not connected, and maintains a state corresponding to the set value, wherein the data output unit outputs the transmission data indicating the set value based on electrical signals acquired from the first transmission line and the second transmission line, respectively.

[0010] The switch control unit further comprises a third switch that switches between a connected state and a disconnected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected, and a second resistor having a resistance value smaller than the resistance value of the first resistor, between the third switch and the first transmission line and between the third switch and the second transmission line. The switch control unit may control the first switch and the third switch to disconnect the third switch when the first switch is in the connected state and the bias voltage is applied to the first transmission line and the second transmission line, and to disconnect the first switch when the third switch is in the connected state and the bias voltage is applied to the first transmission line and the second transmission line.

[0011] The switch control unit may, after a predetermined period of time has elapsed or when the data output circuit starts operating, turn off the first switch and turn on the third switch.

[0012] In a second embodiment of the present invention, a substrate, a first transmission line and a second transmission line formed on the substrate having lands or vias and transmitting an electrical signal when a bias voltage is applied, a bias voltage application unit for applying the bias voltage to the first transmission line and the second transmission line, a first resistor having a predetermined resistance value provided between the bias voltage application unit and the first transmission line and between the bias voltage application unit and the second transmission line, and a switch for switching between a connected state and a disconnected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected, The present invention provides a data output circuit comprising: a second resistor having a resistance value smaller than the resistance value of the first resistor, located between the switch and the first transmission line and between the switch and the second transmission line; a switch control unit that controls the switch to switch whether or not to apply the bias voltage to the first and second transmission lines via the second resistor; and a data output unit connected to the first and second transmission lines that outputs transmission data based on the electrical signals transmitted by the first and second transmission lines, respectively, wherein the switch control unit keeps the switch connected for a predetermined period of time at a predetermined timing.

[0013] In a third aspect of the present invention, a fire alarm terminal connected to a transmission line is provided, comprising: a sensor for detecting a fire; a communication circuit for communicating with a receiver via the transmission line; a data output circuit according to the first aspect; and a terminal control circuit that takes the value indicated by the transmission data output by the data output circuit as the terminal address value of the fire alarm terminal, and controls the fire alarm terminal to perform an operation corresponding to the command value included in the transmission signal when the terminal address value matches the address value included in the transmission signal, wherein the switch control unit connects the first switch in response to the communication circuit receiving the address value, and disconnects the first switch after the data output circuit outputs the terminal address value.

[0014] In a fourth aspect of the present invention, a fire alarm system is provided comprising a plurality of fire alarm terminals of a third form connected to a transmission line, and a receiver that transmits and receives signals with the plurality of fire alarm terminals via the transmission line, wherein the plurality of fire alarm terminals are each set to a different terminal address value, and when the receiver communicates with one fire alarm terminal, it transmits the transmission signal to the transmission line including the address value that matches the terminal address value of the one fire alarm terminal and a command value corresponding to an operation to be performed by the one fire alarm terminal, and the switch control unit connects the first switch in response to receiving the address value transmitted by the receiver, and disconnects the first switch after the data output circuit outputs the terminal address value. [Effects of the Invention]

[0015] According to the present invention, it is possible to suppress the increase in substrate costs while making it less likely for abnormalities to occur due to ion migration. [Brief explanation of the drawing]

[0016] [Figure 1] This document shows an example of the configuration of the fire alarm system S according to this embodiment. [Figure 2] An example of a transmission signal transmitted and received by the receiver 10 according to this embodiment is shown. [Figure 3] An example of a transmission signal transmitted by the receiver 10 according to this embodiment and a response signal transmitted by the fire alarm terminal 100 in response to the transmission signal are shown. [Figure 4] This diagram shows an example of the configuration of the fire alarm terminal 100 according to this embodiment. [Figure 5] An example configuration of a conventional data output circuit 140 is shown. [Figure 6] An example configuration of the data output circuit 300 according to this embodiment is shown. [Figure 7] A first modified example of the data output circuit 300 according to this embodiment is shown. [Figure 8] A second modified example of the data output circuit 300 according to this embodiment is shown.

Mode for Carrying Out the Invention

[0017] <Configuration Example of Fire Alarm System S> FIG. 1 shows a configuration example of a fire alarm system S according to the present embodiment. The fire alarm system S monitors the occurrence of a fire or the like based on the measurement results of a plurality of fire alarm terminals 100. The fire alarm system S includes a receiver 10, a transmission line 20, and a fire alarm terminal 100.

[0018] The receiver 10 is connected to one or more transmission lines 20 and transmits and receives signals to and from a plurality of fire alarm terminals 100 via the transmission line 20. The receiver 10 may further communicate with the fire alarm terminal 100 via a repeater or the like. The receiver 10, for example, collects information such as the occurrence of a fire and the operating status of the terminal from the fire alarm terminal 100 by communicating with the fire alarm terminal 100. At least a part of the receiver 10 is a computer such as a server. The receiver 10 has functions such as generating an alarm based on the collected information and displaying the information. The receiver 10 may also have a function of transmitting information to an external device, server, or the like.

[0019] The fire alarm terminal 100 is connected to the transmission line 20 and measures the state of the environment that changes due to a fire. The fire alarm terminal 100 has, for example, sensors for detecting smoke, heat, flames, etc., and transmits environmental information indicating the detection results of the sensors to the receiver 10 via the transmission line 20. Further, the fire alarm terminal 100 may determine whether a fire has occurred based on the detection results of the sensors and transmit the determination result to the receiver 10 as environmental information. Note that the fire alarm terminal 100 may receive power from the receiver 10 via the transmission line 20. The communication between the receiver 10 and the fire alarm terminal 100 as described above will be described next.

[0020] <An Example of a Transmission Signal> Figure 2 shows an example of a transmission signal transmitted and received by the receiver 10 according to this embodiment. Figure 2 shows an example of polling on the transmission line 20. It is assumed that the fire alarm terminals 100 are each assigned different terminal address values. The receiver 10 then performs polling on the multiple fire alarm terminals 100 in sequence and collects environmental information from each fire alarm terminal 100.

[0021] When the receiver 10 communicates with a fire alarm terminal 100, it sends a transmission signal to the transmission line 20 that includes an address value matching the terminal address value of the fire alarm terminal 100 and a command value corresponding to the operation to be performed by the fire alarm terminal. Figure 2 shows an example in which the receiver 10 performs polling by sending n transmission signals to n fire alarm terminals 100, each with a terminal address set to a value from 01 to n.

[0022] The fire alarm terminal 100 receives such transmission signals sequentially. When the fire alarm terminal 100 receives a transmission signal with an address value that matches its own terminal address, it performs an action corresponding to the command value contained in the received transmission signal. The fire alarm terminal 100 then sends a response signal to the transmission line 20 indicating the result of performing the action corresponding to the command value. Actions corresponding to the command value include, for example, sending the sensor detection result, sending the fire occurrence determination result, sending temperature information inside the terminal, sending information indicating the type of terminal, and sending the operation confirmation result indicating that it is operating normally.

[0023] Figure 2 shows an example in which n fire alarm terminals 100 receive a transmission signal specifying their terminal address, perform the corresponding operation, and send a response signal. The receiver 10 receives the n response signals transmitted by the n fire alarm terminals 100 from the transmission line 20. As a result, the receiver 10 can obtain the operation result of a specified operation from a specified fire alarm terminal 100 among the multiple fire alarm terminals 100 connected to the transmission line 20.

[0024] <An example of a transmission signal and a response signal> Figure 3 shows an example of a transmission signal transmitted by the receiver 10 according to this embodiment and a response signal transmitted by the fire alarm terminal 100 in response to the transmission signal. Figure 3 shows the order in which the data contained in each signal are arranged, and the fire alarm terminal 100 receives the data in this order. The transmission signal may include data such as start, address value, command value, parameter value, check value, stop, etc.

[0025] The "Start" parameter indicates the start of transmission, the "Address" parameter indicates the destination fire alarm terminal 100, and the "Command" parameter indicates the action to be performed by the destination fire alarm terminal 100. The "Parameter" parameter indicates the parameters used in the operation. The "Check" parameter is data for error detection. The "Stop" parameter indicates the end of transmission. Figure 3(a) shows an example where the transmission signal includes data indicating "Start," "Address," "Check," and "Command."

[0026] When the fire alarm terminal 100 receives such a transmission signal, it compares the address value with its own terminal address. Figure 3(b) shows the timing at which the fire alarm terminal 100 performs the comparison operation between the address value and its own terminal address. If the address value and the terminal address match, the fire alarm terminal 100 performs the operation corresponding to the command value and transmits a response signal. For example, the fire alarm terminal 100 performs the comparison operation between the address value and the terminal address during period T3 shown in Figure 3(b), and after period T3, it performs the operation corresponding to the command value.

[0027] The response signal may include data indicating start, parameter value, check value, stop, etc. The parameter value indicates the result of the operation corresponding to the command value. The check value is data for error detection. Stop indicates the end of transmission. Figure 3(a) shows an example in which the response signal includes data indicating parameter value, check value, and stop. The receiver 10 receives the response signal shown in Figure 3(a) by transmitting the transmission signal shown in Figure 3(a). The fire alarm terminal 100 that transmits such a response signal will be described next.

[0028] <Example configuration of fire alarm terminal 100> Figure 4 shows an example of the configuration of a fire alarm terminal 100 according to this embodiment. The fire alarm terminal 100 includes a communication circuit 110, a power supply circuit 120, a sensor 130, a data output circuit 140, a storage unit 150, and a terminal control circuit 160.

[0029] The communication circuit 110 communicates with the receiver 10 via the transmission line 20. The communication circuit 110 receives the transmission signal transmitted by the receiver 10. In addition, if the terminal control circuit 160 performs an operation corresponding to the command value contained in the transmission signal, the communication circuit 110 sends a response signal to the receiver 10.

[0030] The power supply circuit 120 receives power via the transmission line 20 and supplies power voltage or power to each part of the fire alarm terminal 100. The power supply circuit 120 may include, for example, an AC / DC converter, a DC / DC converter, etc. The power supply circuit 120 may also supply a bias voltage to the data output circuit 140.

[0031] Sensor 130 is a sensor for detecting fire. Sensor 130 detects smoke, heat, flames, etc. The data output circuit 140 outputs transmission data indicating the terminal address value of the fire alarm terminal 100 to the terminal control circuit 160. The operation of the data output circuit 140 will be described later.

[0032] The memory unit 150 may store information such as the OS (Operating System) and programs that enable the processor to function when the processor or the like functions as a terminal control circuit 160. The memory unit 150 may also store various information, including a database that is referenced when the program is executed. For example, the processor functions as a terminal control circuit 160 by executing a program stored in the memory unit 150.

[0033] The storage unit 150 includes, for example, a ROM (Read Only Memory) for storing various programs and tables executed by a computer, and a RAM (Random Access Memory) for use as a working area. The storage unit 150 may also include a large-capacity storage device such as an HDD (Hard Disk Drive) and / or an SSD (Solid State Drive).

[0034] The storage unit 150 may store intermediate data, calculation results, thresholds, reference values, and parameters generated (or used) by the fire alarm terminal 100 during its operation. The storage unit 150 may also supply the stored data to the requesting party in response to requests from various parts within the fire alarm terminal 100.

[0035] The terminal control circuit 160 controls each part of the fire alarm terminal 100. For example, the terminal control circuit 160 determines whether the terminal address value indicated by the transmission data output by the data output circuit 140 matches the address value contained in the transmission signal received by the communication circuit 110. If the terminal address value matches the address value contained in the transmission signal, the terminal control circuit 160 controls each part of the fire alarm terminal 100 to execute the operation corresponding to the command value contained in the transmission signal.

[0036] The terminal control circuit 160, as an operation corresponding to the command value, transmits the detection result of the sensor 130 from the communication circuit 110 to the receiver 10. Alternatively, the terminal control circuit 160 may determine whether or not a fire has occurred based on the detection result of the sensor 130 and transmit the determination result from the communication circuit 110 to the receiver 10.

[0037] It is desirable that the fire alarm terminals 100 described above be installed at multiple locations within the building to be monitored for fire. The receiver 10 can then more accurately determine the occurrence of a fire by collecting information transmitted from multiple fire alarm terminals 100. Therefore, the fire alarm system S of this embodiment can reduce the risk of damage caused by fire. Next, the data output circuit 140 used in the fire alarm terminal 100 will be described.

[0038] <Example configuration of conventional data output circuit 140> Figure 5 shows an example of the configuration of a conventional data output circuit 140. The data output circuit 140 is a circuit that outputs transmission data indicating a preset terminal address value. The data output circuit 140 comprises a circuit board, vias 210, a reference potential 220, a transmission line 230, a bias voltage application unit 240, a first resistor 250, a setting switch 260, a buffer 270, and a data output unit 280.

[0039] The substrate is a printed circuit board. The substrate may also be a multilayer substrate. Figure 5 shows an example of the circuit configuration of a data output circuit 140 formed on the substrate. The vias 210 may penetrate the substrate (through vias or through-holes), or they may reach the intermediate layer of the substrate. The vias 210 electrically connect, for example, a conductor on the surface of the substrate to a conductor on the back surface of the substrate and / or inside the substrate.

[0040] The reference potential 220 is the reference potential of the circuit. Figure 5 shows an example where the reference potential 220 is the ground (GND) potential. The transmission line 230 transmits electrical signals with a bias voltage applied. The transmission line 230 is formed to have lands or vias 210 on the surface of the substrate.

[0041] Multiple transmission lines 230 are provided on the circuit board. It is desirable that the circuit board has the same number of transmission lines 230 as the number of bits used to represent the terminal address value. For example, eight transmission lines 230 are provided on the circuit board so that the terminal address value can be set with 8 bits. Figure 5 shows an example in which two of the multiple transmission lines 230 on which vias 210 are formed are designated as the first transmission line 231 and the second transmission line 232.

[0042] The bias voltage application unit 240 applies a bias voltage to the transmission line 230, including the first transmission line 231 and the second transmission line 232. Based on the power supplied from the power supply circuit 120, the bias voltage application unit 240 supplies a bias voltage of a predetermined voltage to each of the transmission lines 230. The bias voltage application unit 240 may include, for example, an AC / DC converter, a DC / DC converter, etc. If the power supply circuit 120 is capable of supplying a predetermined bias voltage, the power supply circuit 120 may function as the bias voltage application unit 240.

[0043] The first resistor 250 is provided between the bias voltage application unit 240 and the transmission line 230. For example, the first resistor 250 is provided between the bias voltage application unit 240 and the first transmission line 231 and functions as a pull-up resistor for the first transmission line 231. Similarly, the first resistor 250 is provided between the bias voltage application unit 240 and the second transmission line 232 and functions as a pull-up resistor for the second transmission line 232. The first resistor 250 has a resistance value of, for example, 1 MΩ to several hundred MΩ.

[0044] The setting switch 260 is provided on each of the transmission lines 230 and is a switch for setting the terminal address value. It is desirable that the setting switch 260 be pre-switched to either the disconnected or connected state by the user of the fire alarm terminal 100, the worker installing the fire alarm terminal 100, the manufacturer that produced the fire alarm terminal 100, etc. The setting switch 260 is, for example, a rotary type or a slide type DIP switch.

[0045] For example, the first setting switch 261 is a switch that switches between a connected state in which the first transmission line 231 is electrically connected to a reference potential and a disconnected state in which it is not connected, and maintains a state corresponding to the set value of the terminal address. For example, if the set value of the terminal address corresponding to the first transmission line 231 is "0", the first setting switch 261 switches to the connected state and maintains that connected state. As a result, the first transmission line 231 transmits low-potential electrical signals.

[0046] Similarly, the second setting switch 262 is a switch that switches between a connected state in which the second transmission line 232 is electrically connected to the reference potential and a disconnected state in which it is not connected, and maintains a state corresponding to the set value of the terminal address. For example, if the set value of the terminal address corresponding to the second transmission line 232 is "1", the second setting switch 262 switches to the disconnected state and maintains that disconnected state. As a result, the first transmission line 231 transmits high-potential electrical signals.

[0047] Buffer 270 is provided for each of the multiple transmission lines 230 and supplies the electrical signals transmitted by the transmission lines 230 to the data output unit 280. The data output unit 280 is connected to each of the multiple transmission lines 230 via buffer 270 and outputs transmission data based on the electrical signals transmitted by each of the multiple transmission lines 230. For example, the data output unit 280 outputs transmission data indicating a set value (01) based on the low potential and high potential electrical signals acquired from the first transmission line 231 and the second transmission line 232, respectively.

[0048] Here, "0" is used as the connection state and "1" as the disconnection state setting values, but this logic is just one example of a setting in circuit design and is not limited to this. The data output circuit 140 may be set with the reverse logic (i.e., "0" as the disconnection state and "1" as the connection state setting values).

[0049] As described above, the data output circuit 140 switches the setting switch 260 according to the set value, which is the terminal address value, and outputs transmission data indicating the set value to the terminal control circuit 160 in response to a request from the terminal control circuit 160. This allows the terminal control circuit 160 to compare the address value contained in the transmission signal with the terminal address value set in the fire alarm terminal 100.

[0050] In this case, the transmission line 230 of the conventional data output circuit 140 remains in a high potential state or a low potential state depending on the set value. For example, if the first transmission line 231 is at a low potential and the second transmission line 232 is at a high potential, a potential difference will persist between the first transmission line 231 and the second transmission line 232.

[0051] In this case, ion migration may occur between the first transmission line 231 and the second transmission line 232, potentially leading to insulation failure. Furthermore, metal growth due to ion migration can occur not only on the surface of the printed circuit board, but also between the fibers of the insulating substrate material inside, and in vias 210 of high-impedance circuits. The conductive bridges (dendrites) formed by the growth of metal are so small that they are difficult to detect with the naked eye, and if they occur inside the substrate, they may not be observable without using special methods such as destructive testing.

[0052] Since many fire alarm terminals 100 are installed in a building, it is desirable to minimize the current consumption per terminal, and they tend to be composed of high-impedance circuits. For example, the first resistor 250 is set to a high resistance value and designed to minimize current consumption. In addition, the installation environment of the fire alarm terminals 100 may be a poorly ventilated, high-humidity environment, such as the underside of the building structure. Furthermore, due to the demand for miniaturization and the increasing complexity of the circuits, the mounting density of the printed circuit boards of the fire alarm terminals 100 tends to increase, and the spacing between patterns and vias 210 tends to narrow. Consequently, fire alarm terminals 100 tend to be prone to circuit abnormalities due to ion migration.

[0053] For example, as described in Patent Document 1, printed circuit boards capable of suppressing ion migration are known and are sometimes used in products that cannot be easily repaired, such as space equipment. However, such printed circuit boards are expensive, which leads to the problem of increasing the cost of the fire alarm terminal 100. Therefore, the fire alarm terminal 100 according to this embodiment suppresses the increase in terminal cost while making it less likely for abnormalities to occur due to ion migration. The data output circuit 300 used in such a fire alarm terminal 100 will be described next.

[0054] <Example configuration of data output circuit 300> Figure 6 shows an example of the configuration of the data output circuit 300 according to this embodiment. The data output circuit 300 has a configuration in which a bias voltage is not applied to the transmission line 230 during periods when it is not performing the operation of outputting transmission data, thereby suppressing the occurrence of ion migration. In the data output circuit 300 according to this embodiment, components that are substantially the same as those in the conventional data output circuit 140 shown in Figure 5 are given the same reference numerals, and redundant explanations are omitted. The data output circuit 300 further comprises a first switch 310, a second switch 320, and a switch control unit 330.

[0055] The first switch 310 switches between a connected state, where the bias voltage application unit 240 and the multiple transmission lines 230 are electrically connected, and a disconnected state, where they are not connected. The first switch 310 is provided between the bias voltage application unit 240 and the first resistor 250. In this case, for example, the first resistor 250 is connected between the first switch 310 and the first transmission line 231, and between the first switch 310 and the second transmission line 232.

[0056] The second switch 320 switches between a connected state, where the reference potential 220 is connected to the multiple transmission lines 230, and a disconnected state, where they are not connected. The first switch 310 and the second switch 320 are semiconductor switches, such as FETs.

[0057] The second switch 320 is controlled to be disconnected when the first switch 310 is connected, and connected when the first switch 310 is disconnected. For example, when the first switch 310 is disconnected, the value of the transmission line 230 becomes undefined and may be susceptible to noise. Therefore, by connecting the second switch 320 when the first switch 310 is disconnected, the value of the transmission line 230 can be fixed to a reference voltage, thereby reducing the effects of noise.

[0058] The switch control unit 330 controls the first switch 310 to switch whether or not to apply a bias voltage to the transmission line 230. For example, when the data output unit 280 acquires electrical signals from multiple transmission lines 230 to output transmission data, the switch control unit 330 connects the first switch 310.

[0059] As a result, multiple transmission lines 230 are connected to the bias voltage application unit 240 via the first resistor 250, allowing electrical signals corresponding to the setting switch 260 to be transmitted to the data output unit 280. For example, the first transmission line 231 transmits a low-potential electrical signal, and the second transmission line 232 transmits a high-potential electrical signal to the data output unit 280. As a result, the data output unit 280 can output transmission data indicating the set value (01) based on the low-potential and high-potential electrical signals obtained from the first transmission line 231 and the second transmission line 232, respectively.

[0060] Then, the switch control unit 330 disconnects the first switch 310 after the data output unit 280 has acquired electrical signals from multiple transmission lines 230. The switch control unit 330 keeps the first switch 310 disconnected until the data output unit 280 begins the operation to output the transmission data.

[0061] As a result, the multiple transmission lines 230 are electrically disconnected from the bias voltage application unit 240, so their potentials become approximately the same. For example, the potential difference between the first transmission line 231 and the second transmission line 232 becomes approximately 0V, which suppresses the occurrence of ion migration between the first transmission line 231 and the second transmission line 232.

[0062] Furthermore, the switch control unit 330 controls the first switch 310 and the second switch 320 to disconnect the second switch 320 when the first switch 310 is connected to apply a bias voltage to the multiple transmission lines 230. When the first switch 310 is disconnected, the switch control unit 330 connects the second switch 320 to connect the multiple transmission lines 230 to the reference potential 220.

[0063] As a result, when the first switch 310 is turned off, the switch control unit 330 can connect the multiple transmission lines 230 to the reference potential 220, ensuring that the potential difference between the transmission lines is 0V. The switch control unit 330 is composed of a processor, for example, similar to the terminal control circuit 160. Note that the terminal control circuit 160 may also have the functions of the switch control unit 330.

[0064] The switch control unit 330 connects the first switch 310 in response to receiving a control signal from the terminal control circuit 160 requesting the output of a terminal address value. In this case, the switch control unit 330 connects the first switch 310 during period T3 shown in Figure 3(b). The switch control unit 330 also disconnects the first switch 310 when it is waiting to receive a control signal from the terminal control circuit 160 requesting the output of a terminal address value. For example, the switch control unit 330 disconnects the first switch 310 during periods T1 and T2 shown in Figure 3(b).

[0065] In other words, the switch control unit 330 connects the first switch 310 in response to the communication circuit 110 of the fire alarm terminal 100 receiving a transmission signal including an address value, and disconnects the first switch 310 after the data output circuit 300 outputs the terminal address value. As a result, the data output circuit 300 can output transmission data indicating a set value to the terminal control circuit 160 in response to a request from the terminal control circuit 160, while suppressing the occurrence of ion migration.

[0066] As described above, the data output circuit 300 according to this embodiment is described in which the transmission line 230 and the bias voltage application unit 240 are electrically disconnected during periods when the circuit is not performing operations to output data for transmission, thereby suppressing the occurrence of ion migration. However, the circuit is not limited to this. The data output circuit 300 may also have a configuration that allows bridges and the like formed by ion migration to be electrically disconnected by electric current.

[0067] For example, the first resistor 250 of the data output circuit 300 has a resistance value that is about 1 / 100 to 1 / 1000 of the resistance value of a conventional pull-up resistor. In this case, the resistance value of the first resistor 250 is, for example, in the range of several tens of kΩ to 1 MΩ. When the first resistor 250 is reduced to about 1 / 100 to 1 / 1000, the magnitude of the current flowing from the bias voltage application section 240 to the transmission line 230 increases by about 100 to 1000 times.

[0068] If a bridge is formed by the potential difference between the two transmission lines 230, a large current will flow through the bridge when the first switch 310 is connected. Because the bridge has a very small shape, such a large current can cause it to overheat and burn out. Therefore, the data output circuit 300 according to this embodiment can electrically disconnect the bridge even if it is formed between the two transmission lines 230 by reducing the resistance value of the first resistor 250.

[0069] In the data output circuit 300 described above, an example was explained in which the wiring connecting the bias voltage application unit 240 and the transmission line 230 (referred to as the bias line) has the function of supplying a bias voltage to the transmission line 230 in order to transmit an electrical signal and the function of electrically disconnecting the bridge. However, the circuit is not limited to this example. The data output circuit 300 may have a separate bias line for transmitting an electrical signal and a separate bias line for electrically disconnecting the bridge. Such a data output circuit 300 will be described next.

[0070] <First modified example of data output circuit 300> Figure 7 shows a first modified example of the data output circuit 300 according to this embodiment. In the data output circuit 300 of the first modified example, components that are substantially the same as those in the data output circuit 300 according to this embodiment shown in Figure 6 are denoted by the same reference numerals, and redundant explanations are omitted. The data output circuit 300 of the first modified example includes two bias lines that supply bias voltage from the bias voltage application unit 240 to a plurality of transmission lines 230.

[0071] The first bias line 340 is a bias line for transmitting electrical signals to the transmission line 230, as described in Figure 5 or Figure 6. Figure 7 shows an example in which the first bias line 340 has a first resistor 250 as shown in Figure 5. Alternatively, the first bias line 340 may be further provided with a first switch 310 and a second switch 320, as described in Figure 6. Since such a first bias line 340 has been described in Figure 5 or Figure 6, its description will be omitted here.

[0072] The second bias line 350 includes a third switch 351 and a second resistor 352. The third switch 351 switches between a connected state, where the bias voltage application unit 240 and the multiple transmission lines 230 are electrically connected, and a disconnected state, where they are not connected. The third switch 351 may be a semiconductor switch such as an FET, similar to the first switch 310 and the second switch 320.

[0073] The second resistor 352 is provided between the third switch 351 and each of the multiple transmission lines 230. For example, the second resistor 352 is provided between the third switch 351 and the first transmission line 231, and between the third switch 351 and the second transmission line 232. In other words, each of the multiple transmission lines 230 is connected to the third switch 351 via the second resistor 352.

[0074] The second resistor 352 has a resistance value smaller than that of the first resistor 250. The second resistor 352 has a resistance value approximately 1 / 100 to 1 / 1000 of that of the first resistor 250. In this case, the resistance value of the second resistor 352 is, for example, in the range of several tens of kΩ to 1 MΩ. This allows the second bias line 350 to have the function of electrically disconnecting the bridge.

[0075] The switch control unit 330 connects the third switch 351 for a predetermined period of time at a predetermined timing. For example, the switch control unit 330 connects the third switch 351 for a predetermined period of time when the data output circuit 300 is not performing the operation of outputting transmission data. In this case, the switch control unit 330 connects the third switch 351 when the predetermined period has elapsed or when the data output circuit 300 starts operating.

[0076] It is desirable for the switch control unit 330 to periodically switch the third switch 351 to the connected state. This allows the data output circuit 300 to electrically disconnect the bridge even if a bridge is formed in the transmission line 230 due to ion migration.

[0077] <Second modified example of data output circuit 300> Figure 8 shows a second modified example of the data output circuit 300 according to this embodiment. In the data output circuit 300 of the second modified example, components that are substantially the same as those in the data output circuit 300 of the first modified example shown in Figure 7 are denoted by the same reference numerals, and redundant explanations are omitted. The data output circuit 300 of the second modified example shows a configuration in which a first switch 310 and a second switch 320 are further provided on the first bias line 340.

[0078] As shown in Figure 8, when a first switch 310 is provided on the first bias line 340, the switch control unit 330 controls the first switch 310 and the third switch 351. For example, when the switch control unit 330 connects the first switch 310 and applies a bias voltage to multiple transmission lines 230, it disconnects the third switch 351. Also, when the switch control unit 330 connects the third switch 351 and applies a bias voltage to multiple transmission lines 230, it disconnects the first switch 310.

[0079] Then, when a predetermined period of time has elapsed, or when the data output circuit 300 starts operating, the switch control unit 330 disconnects the first switch 310 and connects the third switch 351. In this way, when the data output circuit 300 is performing an operation to output transmission data, it does not perform an operation to electrically disconnect the bridge. Conversely, when the data output circuit 300 is not performing an operation to output transmission data, it performs an operation to electrically disconnect the bridge. In this way, since the data output circuit 300 does not perform an operation to output transmission data when the bridge is disconnected, it is possible to prevent noise caused by the bridge disconnection operation from being mixed into the transmission data.

[0080] Furthermore, even if the first bias line 340 is equipped with a first switch 310 and a second switch 320, the switch control unit 330 controls the first switch 310, the second switch 320, and the third switch 351 in the same manner. For example, when the first switch 310 is connected and a bias voltage is applied to multiple transmission lines 230, the switch control unit 330 disconnects the second switch 320 and the third switch 351.

[0081] Furthermore, when the switch control unit 330 connects the third switch 351 and applies a bias voltage to the multiple transmission lines 230, it disconnects the first switch 310 and the second switch 320. When the switch control unit 330 does not apply a bias voltage to the multiple transmission lines 230, it disconnects the first switch 310 and the third switch 351 and connects the second switch 320.

[0082] In the above, we have explained, using the data output circuit 300 of the fire alarm terminal 100 as an example, how ion migration occurring between the two transmission lines 230 can be suppressed and how bridges formed by ion migration can be electrically disconnected, but this is not limited to this. Such suppression of ion migration may be applied to circuits other than the data output circuit 300 of the fire alarm terminal 100.

[0083] For example, in a circuit board with a wiring pattern to which a bias voltage is applied, where a potential difference is generated between adjacent wiring patterns, the occurrence of ion migration can be suppressed as described above. Furthermore, even if a bridge is formed between adjacent wiring patterns, the bridge can be electrically disconnected as described above.

[0084] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. [Explanation of Symbols]

[0085] 10 Receivers 20 transmission lines 100 Fire alarm terminals 110 Communication Circuit 120 Power supply circuit 130 sensors 140 Data output circuit 150 Storage section 160 Terminal control circuit 210 Beer 220 Reference Potential 230 transmission line 231 First transmission line 232 Second transmission line 240 Bias voltage application section 250 1st resistance 260 Setting Switches 261 First setting switch 262 Second setting switch 270 buffers 280 Data Output Section 300 Data Output Circuits 310 First switch 320 Second switch 330 Switch control unit 340 First bias line 350 Second bias line 351 Third switch 352 2nd resistor

Claims

1. circuit board and The substrate is formed to have lands or vias, and transmits electrical signals when a bias voltage is applied, and includes a first transmission line and a second transmission line. A bias voltage application unit for applying the bias voltage to the first transmission line and the second transmission line, A first switch that switches between a connected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected and a disconnected state in which they are not connected, A switch control unit that controls the first switch to switch whether or not to apply the bias voltage to the first transmission line and the second transmission line, A data output unit connected to the first transmission line and the second transmission line, which outputs transmission data based on the electrical signals transmitted by the first transmission line and the second transmission line, respectively. Equipped with, The switch control unit, When the data output unit acquires electrical signals from the first transmission line and the second transmission line in order to output the transmission data, the first switch is connected. The data output unit, after acquiring electrical signals from the first transmission line and the second transmission line, sets the first switch to an off state. Data output circuit.

2. The data output circuit according to claim 1, further comprising a first resistor having a predetermined resistance value between the first switch and the first transmission line, and between the first switch and the second transmission line.

3. The system further includes a second switch that switches between a connected state, where a reference potential is connected to the first transmission line and the second transmission line, and a disconnected state, The switch control unit controls the first switch and the second switch, When the first switch is connected and the bias voltage is applied to the first transmission line and the second transmission line, the second switch is disconnected, When the first switch is turned off, the second switch is turned on to connect the first transmission line and the second transmission line to the reference potential. The data output circuit according to claim 1.

4. A switch for switching between a connected state and a disconnected state in which the first transmission line is electrically connected to a reference potential, comprising a first setting switch that maintains a state corresponding to a set value, A switch that switches between a connected state in which the second transmission line is electrically connected to the reference potential and a disconnected state in which it is not connected, and a second setting switch that maintains a state corresponding to the set value Furthermore, The data output unit outputs the transmission data indicating the set value based on the electrical signals acquired from the first transmission line and the second transmission line, respectively. The data output circuit according to claim 1.

5. A third switch that switches between a connected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected and a disconnected state in which they are not connected, A second resistor having a resistance value smaller than the resistance value of the first resistor is placed between the third switch and the first transmission line, and between the third switch and the second transmission line. Furthermore, The switch control unit controls the first switch and the third switch, When the first switch is connected and the bias voltage is applied to the first and second transmission lines, the third switch is disconnected. When the third switch is connected and the bias voltage is applied to the first transmission line and the second transmission line, the first switch is turned off. The data output circuit according to claim 2.

6. The data output circuit according to claim 5, wherein the switch control unit disconnects the first switch and connects the third switch when a predetermined period of time has elapsed or when the data output circuit starts operating.

7. circuit board and The substrate is formed to have lands or vias, and transmits electrical signals when a bias voltage is applied, and includes a first transmission line and a second transmission line. A bias voltage application unit for applying the bias voltage to the first transmission line and the second transmission line, A first resistor having a predetermined resistance value is provided between the bias voltage application unit and the first transmission line, and between the bias voltage application unit and the second transmission line. A switch that switches between a connected state in which the bias voltage application unit and the first transmission line and the second transmission line are electrically connected and a disconnected state in which they are not connected, Between the switch and the first transmission line, and between the switch and the second transmission line, a second resistor having a resistance value smaller than the resistance value of the first resistor is provided. A switch control unit that controls the switch to switch whether or not to apply the bias voltage to the first transmission line and the second transmission line via the second resistor, A data output unit connected to the first transmission line and the second transmission line, which outputs transmission data based on the electrical signals transmitted by the first transmission line and the second transmission line, respectively. Equipped with, The switch control unit connects the switch for a predetermined period of time at a predetermined timing. Data output circuit.

8. A fire alarm terminal connected to a transmission line, A sensor for detecting fire, A communication circuit that communicates with a receiver via the aforementioned transmission line, The data output circuit according to any one of claims 1 to 6, The terminal control circuit, which controls the fire alarm terminal to perform an action corresponding to the command value contained in the transmission signal, when the value indicated by the transmission data output by the data output circuit is set as the terminal address value of the fire alarm terminal, and when the terminal address value matches the address value contained in the transmission signal received by the communication circuit, Equipped with, The switch control unit connects the first switch in response to the communication circuit receiving the address value, and disconnects the first switch after the data output circuit outputs the terminal address value, in a fire alarm terminal.

9. It is a fire alarm system, A plurality of fire alarm terminals according to claim 8 connected to the transmission line, A receiver that transmits and receives signals to a plurality of fire alarm terminals via the transmission line. Equipped with, Multiple fire alarm terminals are configured with different terminal address values. The aforementioned receiver is When communicating with a fire alarm terminal, the transmission signal including the address value that matches the terminal address value of the fire alarm terminal and a command value corresponding to the operation to be performed by the fire alarm terminal is transmitted to the transmission line. The switch control unit connects the first switch in response to receiving the address value transmitted by the receiver, and disconnects the first switch after the data output circuit outputs the terminal address value. Fire alarm system.

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