Telecommunication device with unused shielded wire

Abstract

To prevent or suppress communication errors in a communication line caused by noise received by a throw-away line in a telecommunication device 1 in which a communication line 5, which is a shielded line used for communicating electric signals, and a throw-away line 6, which is an unused shielded line, are connected.SOLUTION: In a telecommunication device, when a communication line is connected to the telecommunication device and another telecommunication device, and a throw-away line is connected only to the telecommunication device, the length of the throw-away line is equal to or longer than the length at which the upper limit of the noise current generated in the communication line when a specified noise current is applied to the throw-away line satisfies the standard for preventing a specified communication error from occurring in the communication line.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a telecommunication device mounted on or mountable on a vehicle such as an automobile or other machinery, and more particularly to a telecommunication device in which a shielded wire (a signal transmission line with a shield) used for communication of an electrical signal is connected to an unused shielded wire. Here, the telecommunication device may be any device that transmits and receives electrical signals to and from another device in a digital or analog manner through a shielded wire.

Background Art

[0002] In vehicles and other arbitrary machinery, a plurality of telecommunication devices are mounted, and various functions are executed by electrical signals transmitted and received between the telecommunication devices. In this regard, in recent years, with the increasing multifunctionality of machinery such as vehicles, the number of devices for transmitting and receiving electrical signals has increased, and while there are variations in the functions provided for each piece of machinery, if a wire harness (a bundle of signal transmission lines) for communication is prepared for each variation, the manufacturing cost will increase. Also, it is advantageous to be able to easily accommodate post-installation of functions after the machinery is completed or shipped. Therefore, at the time of manufacturing the machinery, a highly versatile wire harness including signal transmission lines not used at the stage of completion or shipment is used to reduce the manufacturing cost, and at the time of post-installing functions, a configuration may be used that enables easy utilization of unused signal transmission lines in the wire harness.

[0003] Regarding unused signal transmission lines (hereinafter referred to as "spur lines") in a wire harness used in a machine tool as described above, various technologies have been proposed. For example, in Patent Document 1, as a vehicle wire harness structure for optimizing the system configuration according to the additional functions and specifications of electrical components, the main control unit is equipped with only the standard processing function for controlling standard in-vehicle electronic devices. However, the functions for controlling each electrical component in the optional in-vehicle electronic device or the additional function in-vehicle electronic device are respectively realized by single-function slave electronic modules provided at the connectors at both ends of the second wire harness or the third wire harness. By selecting the types and numbers of modules to be mounted according to the specifications of the electrical components and functions to be controlled, it is proposed to be able to realize the control functions required by the additional functions at a minimum component cost. Further, in Patent Document 2, regarding the possibility of problems caused by the "spur" circuits included in the wire harness, in order to facilitate the grasp of the situation, among the conduction paths formed by each electric wire constituting the wire harness, for each of the paths between one end connected to some in-vehicle device and the other end connected to another in-vehicle device, the combination of conduction states is sequentially confirmed. When the conduction path is connected only by the "spur" electric wires that are not required by the vehicle specifications from the end on the base point side to the end of the final connection destination, warning information is generated to distinguish it from others. When the conduction path between the end on the base point side and the end of the final connection destination includes a conduction path by the "spur" electric wires that are not required by the vehicle specifications, a configuration is proposed to generate caution information to distinguish it from others.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the connector portion of a wire harness connected to a telecommunications device in a mechanical device such as a vehicle, generally, the GND wires (ground wires) that surround the wires for transmitting signals in each shield wire are electrically connected to each other, and the ground potential is common. In such a wire harness, when both ends of some of the shield wires are connected to the telecommunications device and used for signal communication, and some of the other shield wires are "throw-away wires", since the open ends of the GND wires of the throw-away wires have a high impedance, they function as an antenna that receives electromagnetic noise (radiation, electromotive force) emitted from surrounding devices and the like. Then, the noise received by the throw-away wires is transmitted to the GND wires of the shield wires (hereinafter referred to as "communication wires") that are being used for other signal transmissions, and communication errors may occur in those communication wires. Therefore, in a telecommunications device having throw-away wires, it is preferable that communication errors caused by the noise picked up by the throw-away wires can be prevented or suppressed.

[0006] Thus, one problem of the present invention is to enable prevention or suppression of communication errors in communication wires due to noise received by throw-away wires in a telecommunications device to which throw-away wires are connected.

Means for Solving the Problem

[0007] According to the present invention, the above problem is solved by a telecommunications device in which a communication wire, which is a shield wire used for communication of an electrical signal, and a throw-away wire, which is a shield wire not in use, are connected, the communication wire is connected to the telecommunications device and another telecommunications device, the throw-away wire is not connected to another telecommunications device, and the length of the throw-away wire is such that the upper limit value of the noise current generated in the communication wire when a predetermined noise current is applied to the throw-away wire is equal to or greater than the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication wire.

[0008] In the above configuration, the "shielded wire" is an electric cable configured such that a shield, which is a GND wire, extends along with a signal transmission line for transmitting an electric signal as described above. The "communication line" is a shielded wire whose both ends are connected to different electric communication devices from the above-described electric communication devices, respectively, and the "patch cord" is a shielded wire whose one end is connected to the above-described electric communication device, but the other end is open or not connected to another electric communication device. The "upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line" means a criterion that no arbitrarily set communication error occurs when the communication line receives noise currents at various frequencies, for example, conditions such as no communication error of a predetermined number of bits or more that may be arbitrarily set are satisfied, and is the upper limit value of the noise current, which may be determined for each frequency of the noise. The "upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord" means the upper limit value of the noise current generated in the communication line when a predetermined noise current, which may be appropriately set at various frequencies, is applied to the patch cord. The predetermined magnitude of the noise current applied to the patch cord may be appropriately set according to the intensity of the noise assumed at the site where the electric communication device is installed. Here, the "upper limit value of the noise current generated in the communication line" may be determined for each frequency.

[0009] Generally, in a communication line, the greater the noise current, the more likely communication errors are to occur. Therefore, in order to prevent communication errors in the communication line due to the noise received by the patch cord, the upper limit value of the noise current generated in the communication line due to the noise received by the patch cord should be set to be lower than the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line. In this regard, according to the research by the inventors of the present invention, the magnitude of the noise current generated in the communication line is affected by the length of the patch cord. In particular, it has been experimentally found that the longer the patch cord, the more likely the noise current generated in the communication line due to the noise received by the patch cord tends to decrease. That is, if the length of the patch cord is longer than the length at which the upper limit value of the noise current generated in the communication line due to the noise received by the patch cord becomes the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line, the criterion that no predetermined communication error occurs in the communication line will be satisfied. Thus, in the present invention, as described above, by setting the length of the patch cord to be equal to or greater than the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord becomes the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line, it becomes possible to prevent or suppress communication errors in the communication line due to the noise received by the patch cord.

[0010] In the configuration of the present invention described above, the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line can be determined by changing the noise current at various frequencies in the communication line and checking whether the criterion that no predetermined communication error occurs is satisfied, for example, the communication error is less than 1 bit per data for one image. On the other hand, in determining the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord, first, noise currents are applied to patch cords of various lengths at various frequencies, for example, at frequencies within the range of assumed noise frequencies, and the transmission characteristics for each frequency of the noise current from the patch cord to the communication line are determined for each length of the patch cord. In that case, the transmission characteristics for each frequency tend to have a lower transmittance as the length of the patch cord is longer, but locally, the transmittance of a long patch cord may exceed that of a short patch cord. Therefore, using the transmittance for each frequency of each length of the patch cord, the maximum value of the transmittance for each frequency of the noise current is determined for each length of the patch cord or more, for example, 2 m or more, 3.3 m or more, 5 m or more. Thereafter, by multiplying the maximum value of the transmittance for each frequency of the patch cord of each length or more by a predetermined magnitude of the noise current that may be appropriately set and applied to the patch cord, the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord is calculated for each frequency. Note that the predetermined magnitude of the noise current that may be appropriately set and applied to the patch cord may be equal to or greater than the maximum value of the noise current assumed in the environment where the patch cord is placed, and specifically, it may be the BCI (Bulk Current Injection) test current.

[0011] The length of the patch cord that satisfies the constituent requirements of the present invention described above may be appropriately changed according to the length of the communication line. For example, when the length of the communication line is 7 m, according to experiments, it has been found that a patch cord of 3.3 m or more satisfies the requirements of the present invention described above. Therefore, in the configuration of the present invention described above, when the length of the communication line is 7 m, the length of the patch cord may be 3.3 m or more.

[0012] In the above configuration, it is preferable that the GND line of the communication line and the GND line of the patch cord are electrically disconnected at the connector connected to the telecommunication device. In the case of a general wire harness connected to a telecommunication device, the GND lines of a plurality of shielded lines are electrically connected at the connector connected to the telecommunication device, and the ground potentials are equal. However, the noise received by the patch cord as described above enters the communication line through the GND line. Therefore, by electrically separating the GND line of the patch cord from the GND line of the communication line as described above, communication errors in the communication line due to the noise received by the patch cord can be better prevented or suppressed.

[0013] Also, in the above configuration, the end of the patch cord on the side not connected to the telecommunication device may be connected to the metal body of the mechanical appliance where the telecommunication device is installed via a common-mode resistor or a loss circuit. Here, the metal body of the mechanical appliance may be a metal vehicle body or hull when the mechanical appliance is a vehicle or a moving body. Since the metal body of the mechanical appliance is usually grounded, the noise that has entered the patch cord is converted into thermal energy and attenuated in the common-mode resistor or loss circuit. As a result, communication errors in the communication line due to the noise received by the patch cord can be better prevented or suppressed.

Advantages of the Invention

[0014] Thus, according to the configuration of the present invention described above, in the shielded line of the wire harness connected to the telecommunication device mounted on a mechanical appliance such as a vehicle, when a patch cord is provided, by setting its length to the length that meets the above requirements, it is possible to suppress or prevent communication errors in the communication line due to the noise received by the patch cord. For example, in a vehicle, in recent years, a plurality of cameras are often mounted as an option, and there may be a case where a camera is added later. In that case, if there is a patch cord for the camera control device, it is possible to add a camera without replacing the control device. When such a patch cord exists, according to the present invention, the immunity of the communication line against the noise received by the patch cord can be improved.

[0015] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Description of the Reference Numerals

[0017] 1... Telecommunication device, 2... Electric circuit or electronic circuit, 3... Connector, 4a, 4b... Signal transmission lines, 5... Communication line (shielded line), 6... Patch cord (shielded line), 11... Another telecommunication device, 12... Electric circuit or electronic circuit, 13... Connector, 14... Signal transmission line, 20... Analysis device, 21... Current probe, 22... BCI probe, 30... In-phase resistance, 40... Body of mechanical equipment, 50... Loss circuit, N... Noise, Si... Electric signal, s... Signal transmission line, g... GND line (outer sheath), oc... Connector housing, is... Insulating member

Best Mode for Carrying Out the Invention

[0018] Function of a detachable cord connected to a telecommunications device As schematically depicted in Fig. 1(A), a telecommunication device 1 mounted on a vehicle, a moving body, or other mechanical equipment generally has its electric circuit or electronic circuit 2 and a connector 3 connected to the circuit 2 via signal transmission lines 4a, 4b. A wire harness including a plurality of shielded lines 5, 6 for transmitting and receiving signals between the electric circuit or electronic circuit 12 and the signal transmission line 14 and the connector 13 in another telecommunication device 11 is connected to the connector 3. At this time, in order to ensure the versatility of the wire harness and the expandability of functions in mechanical equipment, in addition to the communication line 5, which is a shielded line connected to another telecommunication device 11 so as to enable signal communication therewith, there may be provided a patch cord 6, which is a shielded line that is not connected to other telecommunication devices and is in a non-used state.

[0019] Regarding the configuration in which the detachable wire 6 exists in the telecommunications device 1 as described above, in the connector 3 of the wire harness connected to the telecommunications device 1, while the GND wires of the shield wires 5 and 6 are connected to a common metal fitting in a normal manner and the ground potential is common, when the end 6a of the detachable wire 6 that is not connected to the telecommunications device 1 becomes an open end, the GND wire of the detachable wire 6 functions as an antenna and it becomes easier to pick up the surrounding electromagnetic noise N. And if the electromagnetic noise N is transmitted to the communication line 6 and the signal transmission line 4a that is electrically connected to it with an intensity N close to the signal Si as schematically depicted in Fig. 1(B), a communication error may occur between the electric circuit or electronic circuit 2 in the telecommunications device 1 and the electric circuit or electronic circuit 12 of another telecommunications device 11.

[0020] Regarding this point, according to the research by the inventors of the present invention, the longer the length of the detachable wire, the lower the intensity of the electromagnetic noise picked up by the detachable wire transmitted to the communication line, and the transmittance of the electromagnetic noise from the detachable wire to the communication line tends to decrease as the frequency of the noise is higher, but it has been found that the peak of the transmittance differs depending on the length of the detachable wire. Also, according to the research by the inventors of the present invention, it has been found that the intensity of the noise that generates a communication error when noise is applied to the communication line depends on the frequency of the noise.

[0021] Suppression or prevention of communication errors due to noise from a detachable cord (a) Overview Based on the above findings, the inventors of the present invention have determined that by setting the length of the patch cord to be "equal to or greater than" the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord satisfies the criterion that no predetermined communication error occurs in the communication line, communication errors in the communication line due to the noise received by the patch cord can be prevented or suppressed in the telecommunication equipment to which the patch cord is connected. Here, the predetermined noise current applied to the patch cord may be set to be equal to or greater than the maximum value of the noise current assumed in the normal usage environment of the telecommunication equipment to which the patch cord is connected, as appropriately set. Further, the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line may specifically be set to the upper limit value of the noise current that does not exceed the frequency of the communication error allowed in the telecommunication equipment. And the "upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord", the "upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line", and further the "lower limit of the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord becomes the upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line" can be experimentally determined in the manner described below.

[0022] (b) Measuring device As schematically shown in Fig. 2, a measuring device for determining the length of the patch cord to prevent or suppress communication errors in the communication line due to the noise received by the patch cord is configured such that, in a state where a communication line 5 that is signal-communicably connected between an arbitrary telecommunication device 1 and another telecommunication device 11 and a patch cord 6 that is not connected to other telecommunication devices are connected, a BCI probe 22 that applies noise to the communication line 5 and the patch cord 6 and a current probe 21 that measures the current in the communication line 5 and the patch cord 6 are attached in accordance with the BCI test method, and the noise injected into the communication line 5 and the patch cord 6 and the flowing current are analyzed by an analysis device 20.

[0023] (c) Measurement of the "upper limit value of the noise current that satisfies the criterion that no predetermined communication error occurs in the communication line" In the measurement of this upper limit value, noise currents of various frequencies are injected into the communication line while changing their intensities. At the same time, communication is executed between two telecommunication devices, and it is determined whether the criterion that no predetermined communication error occurs is satisfied for each frequency. As already mentioned, the larger the noise current, the more likely a communication error is to occur. Therefore, by changing the noise current, the upper limit value that satisfies the criterion that no predetermined communication error occurs can be determined. Figure 3(A) shows a measurement example of the upper limit value of the noise current NI [dBA] that satisfies the criterion that no predetermined communication error occurs for each frequency F [MHz] when the length of the communication line is 7 m. In the illustrated example, the criterion that no predetermined communication error occurs is set to the condition that no communication error occurs even once in a certain communication volume. In this figure, when the noise current is smaller than the line LT (OK), the criterion that no predetermined communication error occurs is satisfied.

[0024] (d) Determination of the "upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the drop wire" In determining this upper limit value, first, noise is injected from the BCI probe into patch cords of various lengths while changing its frequency, and the transmittance of the injected noise to the communication line is measured. Fig. 3(B) shows the transmittance Tn [dB] of noise for each frequency F [MHz] of patch cords of several lengths. As can be understood from the figure, overall, it was observed that the longer the length of the patch cord, the more the transmittance tended to decrease. However, since the transmittance for each individual frequency fluctuated up and down depending on the length, for each range of patch cords longer than each length, for example, patch cords of 2m to 7m, patch cords of 3.3m to 7m, and patch cords of 5m to 7m, the maximum value of the transmittance for each frequency was selected. Then, for each range of patch cords longer than each length, the value obtained by multiplying the maximum value of the transmittance for each frequency by a noise current of a predetermined magnitude is set as the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord. The predetermined magnitude of the noise current may be greater than or equal to the maximum value of the noise current assumed in the environment where the patch cord is actually placed. Specifically, it may be the BCI test current. Therefore, the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord determined here is determined for each range of patch cords longer than each length.

[0025] (e) Determination of "the lower limit of the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord satisfies the criterion that no predetermined communication error occurs in the communication line" In determining the lower limit of this length, within the entire range of noise frequencies (the frequency band of noise that normally occurs), it is determined whether the "upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord" determined in (c) above is lower than the "upper limit value of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line" determined in (b) above. Specifically, for example, referring to FIG. 3(C), for the upper limit value where the length of the patch cord is 2 m or more (2 m ≤ L ≤ 7 m), at some frequencies, the upper limit value exceeds the upper limit value LT of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line described in FIG. 3(A), so the above condition is not satisfied. On the other hand, in the same figure, the upper limit value where the length of the patch cord is 3.3 m or more (3.3 m ≤ L ≤ 7 m) is lower than the upper limit value LT of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line over the entire range of noise frequencies, so the above condition is satisfied. Thus, the "lower limit of the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord becomes the upper limit value of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line" is determined as the length of the shortest patch cord among the cases where the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord is lower than the upper limit value LT of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line over the entire range of noise frequencies.

[0026] (f) Specific example According to the experiments of the inventors of the present invention, when the communication line is 7 m, the lower limit of the length at which the upper limit value of the noise current generated in the communication line when a predetermined noise current is applied to the patch cord becomes the upper limit value of the noise current that satisfies the standard that no predetermined communication error occurs in the communication line was 3.3 m. Therefore, in this embodiment, for a telecommunications device with a 7 m communication line, the patch cord shall be 3.3 m or more. Note that when the communication line is shorter, the length of the patch cord that satisfies the standard that no predetermined communication error occurs in the communication line is reduced.

[0027] Other configurations for suppression or prevention of communication errors due to noise from a detachable cord (a) Separation of GND lines in a wire harness As schematically shown in FIG. 4(A), generally at the connector of a wire harness, the GND line g that serves as the outer skin of the signal transmission line s of each shielded line is electrically connected to each other by the metal fittings of the connector housing oc. However, since the GND lines of each shielded line are electrically conductive within the wire harness in this way, noise from the patch cord is easily transmitted to other shielded lines through the GND line. Therefore, in the present embodiment, further, as shown in FIG. 4(B), at the connector housing oc, the GND lines g of each shielded line may be electrically separated from each other by interposing an insulating member is therebetween. Thereby, it is expected that the amount of noise transmitted from the patch cord to the communication line is reduced.

[0028] (b) Connection of the patch cord to the body of the machine via a common-mode resistor The noise received by the patch cord is transmitted to the communication line and a communication error occurs when the intensity of the transmitted noise is large. Therefore, if the noise received by the patch cord can be attenuated by the patch cord itself, the intensity of the noise transmitted to the communication line is reduced and the communication error is suppressed. Thus, as one aspect for attenuating the noise received by the patch cord, as shown in FIG. 5(A), the patch cord 6 may be connected to the metal part 40 of the body of the machine (such as the vehicle body) where the electric communication device 1 is installed via a common-mode resistor 30. Since the body of the machine is usually grounded, with the above configuration, the noise current received by the patch cord passes through the common-mode resistor 30 and is attenuated as heat energy. Preferably, when the size of the common-mode resistor 30 connected to the patch cord is adjusted so that the impedance at the end of the patch cord is matched to the impedance within the patch cord, there is no reflection of noise at the end of the patch cord, resonance of the noise is suppressed, and it is also advantageous in that the intensity of the noise transmitted to the communication line can be reduced.

[0029] (c) Connection of the patch cord to the body of the machine via a loss circuit As a configuration for attenuating the received noise of the drop wire, as shown in Fig. 5(B), the drop wire 6 may be connected to the metal part 40 of the body of the mechanical appliance (such as the vehicle body of a vehicle) where the telecommunication device 1 is installed via a loss circuit 50 such as a ferrite bead. By connecting the loss circuit 50 to the open end of the drop wire, the noise received by the drop wire is attenuated by the loss circuit 50, and the strength of the noise transmitted to the communication line can be reduced.

[0030] Thus, in this embodiment, when a drop wire is connected to a telecommunication device in addition to the communication line, a configuration for suppressing or preventing the occurrence of communication errors in the communication line due to electromagnetic noise picked up by the drop wire is proposed. According to the teaching of this embodiment, even if a drop wire is connected to a telecommunication device mounted on a mechanical appliance such as a vehicle, the occurrence of communication errors can be suppressed or prevented. Therefore, it becomes easy to use a highly versatile wire harness, or it is expected that the function of the mechanical appliance can be easily expanded.

[0031] The above description has been made in relation to the embodiments of the present invention. However, many modifications and changes are easily possible for those skilled in the art, and the present invention is not limited to only the embodiments illustrated above. It will be apparent that the present invention can be applied to various devices without departing from the concept of the present invention.

Claims

1. An electrical communication device in which a communication line, which is a shielded line used for communication of electrical signals, and a patch cord, which is an unused shielded line, are connected. The communication line is connected to the electrical communication device and another electrical communication device, and the patch cord is not connected to another electrical communication device. The length of the patch cord is such that when a predetermined noise current is applied to the patch cord, the upper limit value of the noise current generated in the communication line satisfies the criterion that no predetermined communication error occurs in the communication line.

2. The electrical communication device according to Claim 1, wherein when the length of the communication line is approximately 7 m, the length of the patch cord is 3.3 m or more.

3. The electrical communication device according to Claim 1, wherein the ground wire of the communication line and the ground wire of the patch cord are electrically separated at a connector connected to the electrical communication device.

4. The electrical communication device according to Claim 1, wherein the end of the patch cord on the side not connected to the electrical communication device is connected to the metal body of the mechanical device in which the electrical communication device is installed via a common-mode resistor.

5. The electrical communication device according to Claim 1, wherein the end of the patch cord on the side not connected to the electrical communication device is connected to the metal body of the mechanical device in which the electrical communication device is installed via a loss circuit.

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