Signal transmission apparatus

Abstract

To suppress increase in circuit scale and a device cost.SOLUTION: A signal transmission apparatus includes a pilot signal generation unit that generates multiple pilot signals of different frequencies as a monitoring pilot signal used to detect abnormal levels in specific frequency bands of an input signal, a demultiplexing unit that demultiplexes the multiple pilot signals of different frequencies, one or more detection units that detect at least two or more pilot signals of the multiple pilot signals of different frequencies by using signals demultiplexed by the demultiplexing unit, a switching unit that switches an output target to output each of the multiple pilot signals of different frequencies demultiplexed by the demultiplexing unit at a predetermined cycle to the one or more detection units, a control unit that controls the switching unit so that the output target of the switching unit and an output destination are connected at a predetermined cycle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a signal transmitting device. [Background technology]

[0002] Conventionally, there is known a signal transmission device that includes a pilot signal generating unit that generates a pilot signal used to detect an abnormality in a processing unit that performs internal processing of an input signal (see, for example, Non-Patent Documents 1 and 2). In such a signal transmission device, when the frequency band of the input signal is wide, multiple pilot signal generating units are provided to generate multiple pilot signals of different bands. The pilot signals are detected inside the signal transmission device and may be used to determine whether an abnormality has been detected in the processing unit along the way. This mechanism is equivalent to the mechanism provided in a receiving device.

[0003] Fig. 11 is a diagram showing an example of the configuration of a conventional signal transmission device 100. Fig. 8 shows, as an example of a signal transmission device, a signal transmission device 100 provided in a communication system to which an FM (Frequency Modulation) batch conversion method is applied. The signal transmission device 100 includes an electric signal branching unit 110, a pilot signal generating unit 120, a multiplexing unit 130, an electric signal abnormality detecting unit 140, an electric signal amplifying unit 150, an FM batch converted signal generating unit 160, an electric-optical converting unit 170, an optical signal amplifying unit 180, an optical signal branching unit 190, a demodulated signal abnormality detecting unit 200, a monitoring unit 210, and an alarm processing unit 220. Note that dotted lines extending from some of the functional units to the monitoring unit 210 represent control signals.

[0004] Signals of a plurality of frequency bands are input to the signal transmitting device 100 as input signals. For example, it is assumed that a signal with a frequency band of 70 to 770 MHz (47 to 864 MHz in Non-Patent Document 1) and a signal with a frequency band of 1000 to 2100 MHz (1000 to 2150 MHz in Non-Patent Document 1) are input to the signal transmitting device 100 as input signals. Note that the frequency bands of the input signals input to the signal transmitting device 100 are only examples. In the following, it is assumed that a signal with a frequency band of 70 to 770 MHz and a signal with a frequency band of 1000 to 2100 MHz are input to the signal transmitting device 100 as input signals. The electric signal branching unit 110 branches an input signal input from outside and outputs the branched signal to the multiplexing unit 130 and the electric signal abnormality detection unit 140. The pilot signal generating unit 120 generates pilot signals with a plurality of different frequencies. The pilot signal generating unit 120 generates, for example, a pilot signal having a frequency near 70 MHz, a pilot signal having a frequency near 885 MHz, and a pilot signal having a frequency near 2100 MHz.

[0005] The multiplexing unit 130 generates a multiplexed signal by multiplexing the input signal branched by the electrical signal branching unit 110 and a plurality of pilot signals output from the pilot signal generating unit 120. The multiplexing unit 130 outputs the generated multiplexed signal to the electrical signal amplifying unit 150. The electrical signal amplifying unit 150 amplifies the multiplexed signal output from the multiplexing unit 130 and outputs it to the FM batch converted signal generating unit 160.

[0006] The electrical signal abnormality detection unit 140 detects an abnormality in the power level of the input signal. The electrical signal abnormality detection unit 140 outputs a detection result indicating the presence or absence of an abnormality in the power level of the input signal to the monitoring unit 210. The FM batch converted signal generation unit 160 performs FM batch conversion on the multiplexed signal amplified by the electrical signal amplification unit 150 to generate an FM batch converted signal which is a wideband FM signal and outputs it to the electrical-optical conversion unit 170 and the monitoring unit 210. The electrical-optical conversion unit 170 converts the FM batch converted signal generated by the FM batch converted signal generation unit 160 into an optical signal and outputs it to the optical signal amplification unit 180 and the monitoring unit 210. The optical signal amplification unit 180 amplifies the optical signal output from the electrical-optical conversion unit 170 and outputs it to the optical signal branching unit 190 and the monitoring unit 210.

[0007] The optical signal branching unit 190 branches the optical signal amplified by the optical signal amplifying unit 180 and outputs the branched signal to the outside and to the demodulated signal abnormality detecting unit 200. The demodulated signal abnormality detecting unit 200 converts the optical signal branched by the optical signal branching unit 190 back into an electrical signal, performs FM demodulation, and then detects the state of the demodulated signal. For example, the state detection performed by the demodulated signal abnormality detecting unit 200 is the detection of an abnormality in the level of the frequency band of a pilot signal included in the input demodulated signal. The demodulated signal abnormality detecting unit 200 outputs information on the measurement level to the monitoring unit 210.

[0008] The monitoring unit 210 detects an abnormality in each functional unit based on each signal output from the electrical signal abnormality detection unit 140, the FM batch converted signal generation unit 160, the electrical-optical conversion unit 170, the optical signal amplification unit 180, and the demodulated signal abnormality detection unit 200. For example, the monitoring unit 210 detects the following abnormalities. The monitoring unit 210 detects an abnormality in the power level of the input carrier signal based on the signal output from the electrical signal abnormality detection unit 140. Furthermore, the monitoring unit 210 detects an abnormality in the center frequency of the input FM batch converted signal based on the signal output from the FM batch converted signal generation unit 160. Furthermore, the monitoring unit 210 detects an abnormality in the optical conversion level in the electrical-optical conversion unit 170 based on the signal output from the electrical-optical conversion unit 170. Furthermore, the monitoring unit 210 detects an abnormality in the optical amplification output based on the signal output from the optical signal amplification unit 180. Furthermore, the monitoring unit 210 compares normal state signal level information stored in the memory with level information of the signal demodulated by the demodulated signal abnormality detection unit 200 to determine an abnormal state. When the monitoring unit 210 detects an abnormality, it causes the alarm processing unit 220 to output an alarm.

[0009] 12 is a diagram showing an example of the configuration of a conventional demodulated signal abnormality detection unit 200. The demodulated signal abnormality detection unit 200 includes an optical-electrical conversion unit 201, a demodulation unit 202, a branching unit 203, and a plurality of detection units 204-1 to 204-3. The optical-electrical conversion unit 201 converts the optical signal branched by the optical signal branching unit 190 into an electrical signal. As a result, the FM batch converted signal is restored. The demodulation unit 202 performs FM demodulation on the electrical signal (FM batch converted signal) converted by the optical-electrical conversion unit 201. As a result, the multiplexed signal output from the multiplexing unit 130 is demodulated.

[0010] The demultiplexing unit 203 demultiplexes the multiplexed signal demodulated by the demodulation unit 202 according to the frequency band. For example, the demultiplexing unit 203 demultiplexes signals in the frequency band of 70 MHz to 770 MHz to detection unit 204-1, signals in the frequency band of 770 MHz to 960 MHz to detection unit 204-2, and signals in the frequency band of 960 MHz to 2100 MHz to detection unit 204-3. The detection units 204-1 to 204-3 detect pilot signals included in the signals demultiplexed by the demultiplexing unit 203. [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] “Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion” ITU-T Rec. J. 185, 2012. [Non-Patent Document 2] “Transmission equipment for multi-channel television signals over optical access networks by sub-carrier multiplexing (SCM)” ITU-T Rec. J. 186, 2008. Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, in a device that needs to detect multiple pilot signals, the number of detectors increases according to the number of pilot signals. Therefore, there is a problem that the circuit scale increases according to the number of pilot signals, and the device cost also increases. Note that this problem is not limited to the signal transmission device that performs FM batch conversion shown in Figure 11, but is a problem common to all signal transmission devices that receive input signals with a wide frequency band.

[0013] In view of the above circumstances, an object of the present invention is to provide a technique capable of suppressing an increase in circuit scale and device costs. [Means for solving the problem]

[0014] One aspect of the present invention is a signal transmission device comprising: a pilot signal generation unit that generates pilot signals of a plurality of different frequencies as monitoring pilot signals used to detect level abnormalities in a specific frequency band in an input signal; a branching unit that branches the pilot signals of the plurality of different frequencies; one or more detection units that detect at least two or more pilot signals of the plurality of pilot signals of different frequencies using the signal branched by the branching unit; a switching unit that switches an output target so that each of the plurality of pilot signals of different frequencies branched by the branching unit is output to the one or more detection units at a predetermined period; and a control unit that controls the switching unit to connect the output target of the switching unit to an output destination at the predetermined period. Effect of the Invention

[0015] The present invention makes it possible to suppress an increase in circuit scale and device costs. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating an example of the configuration of a signal transmitting device according to a first embodiment. [Diagram 2] 4 is a diagram illustrating an example of the configuration of a demodulated signal abnormality detection unit in the first embodiment. [Diagram 3] 4 is a diagram illustrating an example of the configuration of a switching unit in the first embodiment. FIG. [Figure 4] 4A to 4C are diagrams for explaining switching timing control of a switching unit in the signal transmission device of the first embodiment. [Diagram 5] FIG. 11 is a diagram illustrating an example of the configuration of a demodulated signal abnormality detection unit in the second embodiment. [Figure 6]FIG. 11 is a diagram illustrating an example of the configuration of a switching unit in the second embodiment. [Figure 7] 13 is a diagram for explaining switching timing control of a switching unit in a signal transmission device according to a second embodiment. FIG. [Figure 8] FIG. 13 is a diagram illustrating an example of the configuration of a demodulated signal abnormality detection unit in the third embodiment. [Figure 9] FIG. 13 is a diagram illustrating an example of the configuration of a switching unit in the third embodiment. [Figure 10] 13 is a diagram for explaining switching timing control of a switching unit in a signal transmission device according to a third embodiment. FIG. [Figure 11] FIG. 1 is a diagram illustrating an example of the configuration of a conventional signal transmitting device. [Figure 12] FIG. 1 is a diagram illustrating an example of the configuration of a conventional demodulated signal abnormality detection unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) FIG. 1 is a diagram showing a configuration example of a signal transmission device 10 in the first embodiment. An input signal having a wide frequency band is input from the outside to the signal transmission device 10. The input signal input from the outside may be a carrier signal obtained from a video signal, for example. The signal transmission device 10 includes an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, an FM batch converted signal generating unit 16, an electric-optical converting unit 17, an optical signal amplifying unit 18, an optical signal branching unit 19, a demodulated signal abnormality detecting unit 20, a monitoring unit 21, and an alarm processing unit 22. Note that dotted lines extending from some of the functional units to the monitoring unit 21 represent control signals.

[0018] The electric signal branching unit 11, pilot signal generating unit 12, multiplexing unit 13, electric signal abnormality detecting unit 14, electric signal amplifying unit 15, FM batch converted signal generating unit 16, electrical-optical converting unit 17, optical signal amplifying unit 18, optical signal branching unit 19, monitoring unit 21, and alarm processing unit 22 basically perform the same processing as the functional units with the same names shown in Fig. 11 (electric signal branching unit 110, pilot signal generating unit 120, multiplexing unit 130, electric signal abnormality detecting unit 140, electric signal amplifying unit 150, FM batch converted signal generating unit 160, electrical-optical converting unit 170, optical signal amplifying unit 180, optical signal branching unit 190, monitoring unit 210, and alarm processing unit 220). The following mainly describes the differences.

[0019] In order to explain the differences, the premise of pilot signals of different frequencies will be explained. The pilot signal generating unit 12 has a function of generating pilot signals of different frequencies. The pilot signals generated by the pilot signal generating unit 12 are monitoring signals used to detect abnormal levels of specific frequency bands in the input signal. In the following explanation, the input signal will be explained as including a signal in a frequency band of 70 to 770 MHz and a signal in a frequency band of 1000 to 2100 MHz. In this way, an input signal with a wide frequency band is input to the signal transmitting device 10.

[0020] The pilot signal generating unit 12 generates a first pilot signal, a second pilot signal, and a third pilot signal to detect abnormal levels of a plurality of frequency bands included in the input signal. For example, the first pilot signal is a pilot signal having a frequency near 70 MHz, the second pilot signal is a pilot signal having a frequency near 885 MHz, and the third pilot signal is a pilot signal having a frequency near 2100 MHz. The pilot signal generating unit 12 only needs to generate a pilot signal having a frequency near the frequency of the input signal, and the frequency of the pilot signal is not limited to the above frequencies. Note that each of the above pilot signals may be generated by one pilot signal generating unit 12, or may be generated by a plurality of pilot signal generating units 12.

[0021] The demodulated signal abnormality detection unit 20 receives an optical signal branched by the optical signal branching unit 19. The demodulated signal abnormality detection unit 20 converts the input optical signal back into an electrical signal and performs FM demodulation, and then detects each pilot signal included in the demodulated signal at different timings. For example, the demodulated signal abnormality detection unit 20 detects a first pilot signal at a certain time a, detects a second pilot signal at a certain time b, and detects a third pilot signal at a certain time c. In this way, the demodulated signal abnormality detection unit 20 shares the detection unit by controlling the timing of detecting the pilot signals. In the following description, the times a, b, and c are assumed to be at the same time interval, but the times a, b, and c may be at different time intervals.

[0022] 2 is a diagram showing an example of the configuration of the demodulated signal abnormality detection unit 20 in the first embodiment. The demodulated signal abnormality detection unit 20 includes an optical-electrical conversion unit 31, a demodulation unit 32, a branching unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36.

[0023] The optical-electrical converter 31 converts the optical signal branched by the optical signal branching unit 19 into an electrical signal.

[0024] The demodulation unit 32 performs FM demodulation on the electrical signal (for example, the FM batch converted signal) converted by the optical-electrical conversion unit 31. In this way, the multiplexed signal output from the multiplexing unit 13 is demodulated.

[0025] The demultiplexing unit 33 demultiplexes the multiplexed signal demodulated by the demodulation unit 32 according to the frequency band. For example, the demultiplexing unit 33 demultiplexes into a signal in a frequency band of 70 MHz to 770 MHz, a signal in a frequency band of 770 MHz to 960 MHz, and a signal in a frequency band of 960 MHz to 2100 MHz. The demultiplexing unit 33 outputs the demultiplexed signals in each frequency band to the switching unit .

[0026] The switching unit 34 switches the output target and output destination of the signal of each frequency band output from the demultiplexing unit 33 under the control of the control unit 36. The switching unit 34 switches the path so that the output target instructed (instructed to switch) by the control unit 36 ​​is output from the instructed output destination, for example.

[0027] The detection units 35-1 to 35-2 receive as input the signals output from the switching unit 34. The detection units 35-1 to 35-2 detect pilot signals included in the input signals. For example, the detection unit 35-1 detects a first pilot signal (pilot signal [1] in FIG. 2), and the detection unit 35-2 detects a second pilot signal and a third pilot signal (pilot signal [2] and pilot signal [3] in FIG. 2). In this way, the detection unit 35-2 detects pilot signals included in the processable frequency range in the input signal.

[0028] The detectors 35-1 to 35-2 may be configured to perform asynchronous detection or synchronous detection. When the switch 34 operates in synchronization with the pilot signal generator 12, the detectors 35-1 to 35-2 may be configured to perform asynchronous detection.

[0029] The control unit 36 ​​controls the pilot signal generating unit 12 and the switching unit 34. When there is no need to synchronize with the generation cycle of the pilot signal by the pilot signal generating unit 12, the control unit 36 ​​only needs to control the switching unit 34. In the following explanation, it is assumed that there is a need to synchronize with the generation cycle of the pilot signal by the pilot signal generating unit 12. The control unit 36 ​​is, for example, a microcomputer.

[0030] The control unit 36 ​​changes the frequency of the pilot signal generated by the pilot signal generating unit 12 at a predetermined period. For example, the control unit 36 ​​causes the pilot signal generating unit 12 to generate a first pilot signal at a certain time a, causes the pilot signal generating unit 12 to generate a second pilot signal at a certain time b, and causes the pilot signal generating unit 12 to generate a third pilot signal at a certain time c. Furthermore, the control unit 36 ​​outputs a switching instruction to the switching unit 34 to switch the output target and output destination of the signal of each frequency band input to the switching unit 34. The switching instruction is an instruction to switch the path so as to connect the output target of the switching unit 34 with the output destination, and includes information indicating, for example, an input terminal to which the signal to be output is input and an output terminal which is the output destination.

[0031] For example, at a certain time a, the control unit 36 ​​switches the path to connect the input terminal to which a signal in a frequency band including a first pilot signal is input as the output target of the switching unit 34 and the output terminal to which the detection unit 35-1 is connected as the output destination, and at time b, switches the path to connect the input terminal to which a signal in a frequency band including a second pilot signal is input as the output target of the switching unit 34 and the output terminal to which the detection unit 35-2 is connected as the output destination, and at time c, switches the path to connect the input terminal to which a signal in a frequency band including a third pilot signal is input as the output target of the switching unit 34 and the output terminal to which the detection unit 35-2 is connected as the output destination.

[0032] FIG. 3 is a diagram showing a configuration example of the switching unit 34 in the first embodiment. As shown in FIG. 3, the switching unit 34 includes a switch unit 341. The switch unit 341 includes a plurality of input terminals 342 to 344, a connection unit 345, and a plurality of output terminals 346 to 347. The switch unit 341 connects any one of the input terminals to any one of the output terminals via the connection unit 345 in response to a switching instruction from the control unit 36. As a result, the switching unit 34 outputs the signals of each frequency band demultiplexed by the demultiplexing unit 33 to the output destination at a predetermined period. In the example shown in FIG. 3, a signal of a frequency band including a first pilot signal demultiplexed by the demultiplexing unit 33 is input to the input terminal 342, a signal of a frequency band including a second pilot signal demultiplexed by the demultiplexing unit 33 is input to the input terminal 343, and a signal of a frequency band including a third pilot signal demultiplexed by the demultiplexing unit 33 is input to the input terminal 344.

[0033] By connecting input terminal 342 and output terminal 346, switching unit 34 outputs a signal in a frequency band including a first pilot signal to detection unit 35-1 connected to output terminal 346. By connecting input terminal 343 and output terminal 347, switching unit 34 outputs a signal in a frequency band including a second pilot signal to detection unit 35-2 connected to output terminal 347. By connecting input terminal 344 and output terminal 347, switching unit 34 outputs a signal in a frequency band including a third pilot signal to detection unit 35-2 connected to output terminal 347.

[0034] FIG. 4 is a diagram for explaining the switching timing control of the switching unit 34 in the signal transmission device 10 of the first embodiment. In FIG. 4, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In FIG. 4, the horizontal axis represents time t, and the vertical axis represents the operation timing of the detection unit 35. As shown in FIG. 4, the control unit 36 ​​controls the switching unit 34 at time a to connect the input terminal 342 and the output terminal 346. As a result, the switching unit 34 switches the connection so that the input terminal 342 and the output terminal 346 are connected during the period of time a, and outputs the signal input to the input terminal 342 to the detection unit 35-1. As a result, the detection unit 35-1 detects the first pilot signal using the signal output from the switching unit 34 during the period of time a.

[0035] Next, when the period of time b begins, the control unit 36 ​​controls the switching unit 34 to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34 switches the connection so that the input terminal 343 and the output terminal 347 are connected during the period of time b, and outputs the signal input to the input terminal 343 to the detection unit 35-2. As a result, the detection unit 35-2 detects the second pilot signal using the signal output from the switching unit 34 during the period of time b.

[0036] Next, at the time period c, the control unit 36 ​​controls the switching unit 34 to connect the input terminal 344 and the output terminal 347. As a result, the switching unit 34 switches the connection so that the input terminal 344 and the output terminal 347 are connected during the time period c, and outputs the signal input to the input terminal 344 to the detection unit 35-2. As a result, the detection unit 35-2 detects the third pilot signal using the signal output from the switching unit 34 during the time period c.

[0037] Note that the operation shown in FIG. 4 is just one example, and when the detection unit 35-1 detects multiple pilot signals of different frequencies, the control unit 36 ​​controls the switching unit 34 so that a signal of a frequency band including the pilot signal detected by the detection unit 35-1 is output to the detection unit 35-1.

[0038] According to the signal transmission device 10 configured as above, the control unit 36 ​​shifts the timing of outputting a signal of a frequency band including a pilot signal to be output by the switching unit 34 so that pilot signals of different frequencies are detected by one detection unit 35. As a result, in a specific time period, a time period in which a pilot signal of a certain frequency does not exist occurs, but if continuous monitoring is not performed, multiple pilot signals can be processed by one detection unit 35, so the number of detection units 35 can be reduced. In the video transmission system, although it is applied to services with very strict monitoring conditions, it can be sufficiently applied by shortening the time interval. In this way, pilot signals of different frequencies are detected at different timings by one detection unit 35, so that the increase in circuit scale corresponding to the increase in the number of pilot signals can be suppressed more than before. As a result, the device cost can also be suppressed.

[0039] Second embodiment In the first embodiment, a configuration is shown in which the signals of each frequency band separated by the branching unit are switched in order by the switching unit and output to the detection unit to be processed. In the second embodiment, a configuration is described in which some detection units constantly monitor signals of a specific frequency band, and other detection units monitor the signals of each frequency band separated by the branching unit by switching them to the switching unit at a specific period. Note that the configuration of the signal transmission device in the second embodiment is the same as that of the first embodiment. The second embodiment differs from the first embodiment in the configuration of the demodulated signal abnormality detection unit. The following mainly describes the differences.

[0040] 5 is a diagram showing an example of the configuration of the demodulated signal abnormality detection unit 20a in the second embodiment. The demodulated signal abnormality detection unit 20a includes an optical-electrical conversion unit 31, a demodulation unit 32, a branching unit 33a, a switching unit 34a, a plurality of detection units 35-1 to 35-2, and a control unit 36a.

[0041] The demultiplexing unit 33a demultiplexes the multiplexed signal demodulated by the demodulation unit 32 according to the frequency band. For example, the demultiplexing unit 33a demultiplexes into a signal in a frequency band of 70 MHz to 770 MHz, a signal in a frequency band of 770 MHz to 960 MHz, and a signal in a frequency band of 960 MHz to 2100 MHz. The demultiplexing unit 33a outputs the demultiplexed signal in a specific frequency band to the detection unit 35-1, and outputs signals in other frequency bands to the switching unit 34a. For example, the demultiplexing unit 33a outputs the demultiplexed signal in a frequency band of 70 MHz to 770 MHz to the detection unit 35-1, and outputs signals in a frequency band of 770 MHz to 960 MHz and signals in a frequency band of 960 MHz to 2100 MHz to the switching unit 34a.

[0042] The switching unit 34a switches between the output target and the output destination of the signal of each frequency band output from the demultiplexing unit 33a under the control of the control unit 36a. For example, the switching unit 34a switches the path so that the output target instructed (instructed to switch) by the control unit 36a is output from the instructed output destination.

[0043] The control unit 36a controls the pilot signal generating unit 12 and the switching unit 34a. When there is no need to synchronize with the generation cycle of the pilot signal by the pilot signal generating unit 12, the control unit 36a only needs to control the switching unit 34a. The control unit 36a is, for example, a microcomputer.

[0044] The control unit 36a changes the frequency of the pilot signal generated by the pilot signal generating unit 12 at a predetermined period. For example, the control unit 36a causes the pilot signal generating unit 12 to generate a first pilot signal at a certain time a, causes the pilot signal generating unit 12 to generate a second pilot signal at a certain time b, and causes the pilot signal generating unit 12 to generate a third pilot signal at a certain time c. Furthermore, the control unit 36a outputs a switching instruction to the switching unit 34a to switch the output target and output destination of the signals of each frequency band input to the switching unit 34a.

[0045] For example, at a certain time a, the control unit 36a switches the path to connect an input terminal to which a signal in a frequency band including the second pilot signal is input as the output target of the switching unit 34a, and an output terminal to which the detection unit 35-2 is connected as the output destination, and at a certain time b, switches the path to connect an input terminal to which a signal in a frequency band including the third pilot signal is input as the output target of the switching unit 34a, and an output terminal to which the detection unit 35-2 is connected as the output destination.

[0046] 5, the branching unit 33a is connected to the detection unit 35-1 without the switching unit 34a. In this way, in the second embodiment, the signal of the specific frequency band output from the branching unit 33a is input to the detection unit 35-1. As a result, the detection unit 35-1 constantly monitors the input signal of the specific frequency band.

[0047] Fig. 6 is a diagram showing an example of the configuration of the switching unit 34a in the second embodiment. As shown in Fig. 6, the switching unit 34a includes a switch unit 341a. The switch unit 341a is composed of a plurality of input terminals 343 to 344 and an output terminal 347. The switch unit 341a connects any one of the input terminals to the output terminal in response to a switching instruction from the control unit 36a. As a result, the switching unit 34a outputs the signals of each frequency band demultiplexed by the demultiplexing unit 33a to the output destination at a predetermined period.

[0048] 6, a signal in a frequency band including the second pilot signal separated by the branching unit 33a is input to the input terminal 343, and a signal in a frequency band including the third pilot signal separated by the branching unit 33a is input to the input terminal 344. The switching unit 34a connects the input terminal 343 and the output terminal 347, thereby outputting the signal in the frequency band including the second pilot signal to the detection unit 35-2 connected to the output terminal 347. The switching unit 34a connects the input terminal 344 and the output terminal 347, thereby outputting the signal in the frequency band including the third pilot signal to the detection unit 35-2 connected to the output terminal 347.

[0049] FIG. 7 is a diagram for explaining the switching timing control of the switching unit 34a in the signal transmission device 10 of the second embodiment. In FIG. 7, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In FIG. 7, the horizontal axis represents time t, and the vertical axis represents the operation timing of the detection unit 35. As shown in FIG. 5, the branching unit 33a and the detection unit 35-1 are directly connected. Therefore, a signal in a frequency band including the first pilot signal is always output to the detection unit 35-1. Therefore, the detection unit 35-1 always detects the first pilot signal using the signal output from the branching unit 33a.

[0050] At time a, the control unit 36a controls the switching unit 34a to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34a switches the connection so that the input terminal 343 and the output terminal 347 are connected during the period of time a, and outputs the signal input to the input terminal 343 to the detection unit 35-2. As a result, the detection unit 35-2 detects the second pilot signal using the signal output from the switching unit 34a during the period of time a.

[0051] Next, at the time period b, the control unit 36a controls the switching unit 34a to connect the input terminal 344 and the output terminal 347. As a result, the switching unit 34a switches the connection so that the input terminal 344 and the output terminal 347 are connected during the time period b, and outputs the signal input to the input terminal 344 to the detection unit 35-2. As a result, the detection unit 35-2 detects the third pilot signal using the signal output from the switching unit 34a during the time period b.

[0052] In the second embodiment, compared to the first embodiment, signals of two frequency bands are input to the switching unit 34a. Therefore, when the period of time c, which is the third timing, arrives, the control unit 36a controls the switching unit 34a to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34a switches the connection so that the input terminal 343 and the output terminal 347 are connected during the period of time c, and outputs the signal input to the input terminal 343 to the detection unit 35-2. As a result, the detection unit 35-2 detects the third pilot signal using the signal output from the switching unit 34a during the period of time c. After that, the control unit 36a switches the connection of the switching unit 34a at regular intervals every time time passes, and causes the signals output from the branching unit 33a to be output in order.

[0053] Note that the operation shown in FIG. 7 is just one example. When the detection unit 35-1 detects multiple pilot signals of different frequencies and the branching unit 33a and the detection unit 35-2 are directly connected, the control unit 36a controls the connection of the switching unit 34a to switch over time so that a signal of a frequency band including the pilot signal detected by the detection unit 35-1 is output to the detection unit 35-1.

[0054] According to the signal transmission device 10a configured as above, among the multiple detection units 35, one detection unit 35 (e.g., detection unit 35-1) constantly monitors signals in a specific frequency band, and one detection unit 35 (e.g., detection unit 35-2) processes signals in other frequency bands at different timings. In this way, while constantly monitoring signals in a specific frequency band, the timing of outputting signals in a frequency band including a pilot signal to be output by the switching unit 34 is shifted so that pilot signals of different frequencies are detected in one detection unit 35 as in the first embodiment. This makes it possible to reduce the number of detection units 35, and to suppress an increase in the circuit scale according to an increase in the number of pilot signals more than in the past. As a result, the device cost can also be suppressed.

[0055] (Third embodiment) In the third embodiment, a configuration will be described in which the signals of each frequency band separated by the branching unit are switched in order by a switching unit and output to one detection unit in order. Note that the configuration of the signal transmission device in the third embodiment is the same as that of the first embodiment. The third embodiment differs from the first embodiment in the configuration of the demodulated signal abnormality detection unit. The following description will focus on the differences.

[0056] 8 is a diagram showing an example of the configuration of a demodulated signal abnormality detection unit 20b in the third embodiment. The demodulated signal abnormality detection unit 20b includes an optical-electrical conversion unit 31, a demodulation unit 32, a branching unit 33, a switching unit 34b, a detection unit 35, and a control unit 36b.

[0057] The switching unit 34b, under the control of the control unit 36b, switches the output target of the signal of each frequency band output from the demultiplexing unit 33. The switching unit 34b switches the path so that the output target instructed (switching instruction) by the control unit 36b is output to the detection unit 35, for example.

[0058] The control unit 36b controls the pilot signal generating unit 12 and the switching unit 34b. When there is no need to synchronize with the generation cycle of the pilot signal by the pilot signal generating unit 12, the control unit 36b only needs to control the switching unit 34b. The control unit 36b is, for example, a microcomputer.

[0059] The control unit 36b changes the frequency of the pilot signal generated by the pilot signal generating unit 12 at a predetermined period. For example, the control unit 36b causes the pilot signal generating unit 12 to generate a first pilot signal at a certain time a, causes the pilot signal generating unit 12 to generate a second pilot signal at a certain time b, and causes the pilot signal generating unit 12 to generate a third pilot signal at a certain time c. Furthermore, the control unit 36b outputs a switching instruction to the switching unit 34b to switch the output target and output destination of the signals of each frequency band input to the switching unit 34b.

[0060] For example, at a certain time a, the control unit 36b switches the path to connect an input terminal to which a signal in a frequency band including a first pilot signal is input as an output target of the switching unit 34b, and an output terminal to which the detection unit 35 is connected as an output destination; at a time b, the control unit 36b switches the path to connect an input terminal to which a signal in a frequency band including a second pilot signal is input as an output target of the switching unit 34b, and an output terminal to which the detection unit 35 is connected as an output destination; and at a time c, the control unit 36b switches the path to connect an input terminal to which a signal in a frequency band including a third pilot signal is input as an output target of the switching unit 34b, and an output terminal to which the detection unit 35 is connected as an output destination.

[0061] In this way, in the third embodiment, the signals of each frequency band output from the branching unit 33 are output in sequence from the switching unit 34b to one detection unit 35. As a result, the detection unit 35 monitors the input signals of the frequency band in sequence.

[0062] Fig. 9 is a diagram showing an example of the configuration of the switching unit 34b in the third embodiment. As shown in Fig. 9, the switching unit 34b includes a switch unit 341b. The switch unit 341b is composed of a plurality of input terminals 342 to 344 and an output terminal 348. The switch unit 341b connects any one of the input terminals to the output terminal in response to a switching instruction from the control unit 36b. As a result, the switching unit 34b outputs the signals of each frequency band demultiplexed by the demultiplexing unit 33 to the output destination at a predetermined period.

[0063] In the example shown in FIG. 9, a signal in a frequency band including a first pilot signal separated by the branching unit 33 is input to the input terminal 342, a signal in a frequency band including a second pilot signal separated by the branching unit 33 is input to the input terminal 343, and a signal in a frequency band including a third pilot signal separated by the branching unit 33 is input to the input terminal 344. The switching unit 34b connects the input terminal 342 and the output terminal 348 to output the signal in the frequency band including the first pilot signal to the detection unit 35 connected to the output terminal 348. The switching unit 34b connects the input terminal 343 and the output terminal 348 to output the signal in the frequency band including the second pilot signal to the detection unit 35 connected to the output terminal 348. The switching unit 34b connects the input terminal 344 and the output terminal 348 to output the signal in the frequency band including the third pilot signal to the detection unit 35 connected to the output terminal 348.

[0064] Fig. 10 is a diagram for explaining the switching timing control of the switching unit 34b in the signal transmission device 10 of the third embodiment. In Fig. 10, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In Fig. 10, the horizontal axis represents time t, and the vertical axis represents the operation timing of the detection unit 35.

[0065] At time a, the control unit 36b controls the switching unit 34b to connect the input terminal 342 and the output terminal 348. As a result, the switching unit 34b switches the connection so that the input terminal 342 and the output terminal 348 are connected during the period of time a, and outputs the signal input to the input terminal 342 to the detection unit 35. As a result, the detection unit 35 detects the first pilot signal using the signal output from the switching unit 34b during the period of time a.

[0066] Next, when the period of time b begins, the control unit 36b controls the switching unit 34b to connect the input terminal 343 and the output terminal 348. As a result, the switching unit 34b switches the connection so that the input terminal 343 and the output terminal 348 are connected during the period of time b, and outputs the signal input to the input terminal 343 to the detection unit 35. As a result, the detection unit 35 detects the second pilot signal using the signal output from the switching unit 34b during the period of time b.

[0067] Next, at the time period c, the control unit 36b controls the switching unit 34b to connect the input terminal 344 and the output terminal 348. As a result, the switching unit 34b switches the connection so that the input terminal 344 and the output terminal 348 are connected during the time period c, and outputs the signal input to the input terminal 344 to the detection unit 35. As a result, the detection unit 35 detects the third pilot signal using the signal output from the switching unit 34b during the time period c.

[0068] According to the signal transmitting device 10b configured as above, the control unit 36b sequentially switches the signals to be input to one detection unit 35 by using the switching unit 34b. In this way, in the third embodiment, one detection unit 35 processes all pilot signals generated by the pilot signal generation unit 12. This makes it possible to reduce the number of detection units 35, and makes it possible to suppress an increase in circuit size in accordance with an increase in the number of pilot signals more than in the past. As a result, the device cost can also be suppressed.

[0069] (Modification 1 common to the first to third embodiments) The signal transmission device 10 in each of the above-mentioned embodiments is configured to perform FM batch conversion and conversion to an optical signal, but the signal transmission device 10 may be a signal transmission device that transmits an electric signal. In this case, the signal transmission device 10 in the first embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, a demodulated signal abnormality detecting unit 20, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the demodulated signal abnormality detecting unit 20. The demodulated signal abnormality detecting unit 20 includes a branching unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36. The branching unit 33 branches the multiplexed signal output from the electric signal amplifying unit 15 according to the frequency band. The demultiplexing unit 33 outputs the demultiplexed signals of each frequency band to the switching unit 34. In this case, the demodulated signal abnormality detecting unit 20 does not need to convert the optical signal into an electrical signal and does not need to perform FM demodulation.

[0070] In addition, when the multiplexed signal output from the electrical signal amplifier 15 is output to the outside, the signal transmitter 10 may include an electrical signal branching unit instead of the optical signal branching unit 19. The electrical signal branching unit branches the input multiplexed signal and outputs it to the outside and to the demodulated signal abnormality detection unit 20. The demodulated signal abnormality detection unit 20 inputs the multiplexed signal branched by the electrical signal branching unit. The demodulated signal abnormality detection unit 20 performs state detection using the input multiplexed signal. In this case, the demodulated signal abnormality detection unit 20 does not need to convert the optical signal to an electrical signal or perform FM demodulation.

[0071] The signal transmission device 10 in the second embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, a demodulated signal abnormality detecting unit 20a, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs the amplified signal to the demodulated signal abnormality detecting unit 20a. The demodulated signal abnormality detecting unit 20a includes a branching unit 33a, a switching unit 34a, a plurality of detection units 35-1 to 35-2, and a control unit 36a. The branching unit 33a branches the multiplexed signal output from the electric signal amplifying unit 15 according to the frequency band. The branching unit 33a outputs the branched signal of a specific frequency band to the detection unit 35-1, and outputs the signals of other frequency bands to the switching unit 34a. In this case, the demodulated signal abnormality detection unit 20a does not need to convert the optical signal into an electrical signal and does not need to perform FM demodulation.

[0072] In addition, when the multiplexed signal output from the multiplexing unit 13 is output to the outside, the signal transmitting device 10 in the second embodiment may include an electric signal branching unit instead of the optical signal branching unit 19. The electric signal branching unit branches the input multiplexed signal and outputs it to the outside and the demodulated signal abnormality detection unit 20a. The demodulated signal abnormality detection unit 20a inputs the multiplexed signal branched by the electric signal branching unit. The demodulated signal abnormality detection unit 20a performs state detection using the input multiplexed signal. In this case, the demodulated signal abnormality detection unit 20a does not need to convert the optical signal to an electric signal and does not need to perform FM demodulation.

[0073] The signal transmission device 10 in the third embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, a demodulated signal abnormality detecting unit 20b, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the demodulated signal abnormality detecting unit 20b. The demodulated signal abnormality detecting unit 20b includes a branching unit 33, a switching unit 34b, a detection unit 35, and a control unit 36b. The branching unit 33 branches the multiplexed signal output from the electric signal amplifying unit 15 according to the frequency band. The branching unit 33 outputs the branched signals of each frequency band to the switching unit 34b. In this case, the demodulated signal abnormality detecting unit 20b does not need to convert the optical signal to an electric signal and FM demodulate.

[0074] In addition, when the multiplexed signal output from the multiplexing unit 13 is output to the outside, the signal transmitting device 10 in the second embodiment may include an electric signal branching unit instead of the optical signal branching unit 19. The electric signal branching unit branches the input multiplexed signal and outputs it to the outside and the demodulated signal abnormality detection unit 20a. The demodulated signal abnormality detection unit 20b inputs the multiplexed signal branched by the electric signal branching unit. The demodulated signal abnormality detection unit 20b performs state detection using the input multiplexed signal. In this case, the demodulated signal abnormality detection unit 20b does not need to convert the optical signal to an electric signal and does not need to perform FM demodulation.

[0075] (Modification 2 common to the first to third embodiments) Although the signal transmission device 10 in each of the above-mentioned embodiments is configured to perform FM batch conversion, the signal transmission device 10 may be a signal transmission device that does not perform FM batch conversion. When configured in this way, the signal transmission device 10 in the first embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, an electric-optical converting unit 17, a demodulated signal abnormality detecting unit 20, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the electric-optical converting unit 17. The electric-optical converting unit 17 converts the multiplexed signal amplified by the electric signal amplifying unit 15 into an optical signal and outputs it to the demodulated signal abnormality detecting unit 20 and the monitoring unit 21. The demodulated signal abnormality detection unit 20 includes an optical-electrical conversion unit 31, a branching unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36. The optical-electrical conversion unit 31 converts the optical signal converted by the electrical-optical conversion unit 17 into an electrical signal. The optical-electrical conversion unit 31 outputs the converted electrical signal to the branching unit 33. The branching unit 33 branches the electrical signal output from the optical-electrical conversion unit 31 according to frequency bands. The branching unit 33 outputs the branched signals of each frequency band to the switching unit 34. If the signal transmission device 10 does not perform FM batch conversion, the demodulated signal abnormality detection unit 20 does not need to perform FM demodulation.

[0076] The signal transmission device 10 in the second embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, an electric-optical converting unit 17, a demodulated signal abnormality detecting unit 20a, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the electric-optical converting unit 17. The electric-optical converting unit 17 converts the multiplexed signal amplified by the electric signal amplifying unit 15 into an optical signal and outputs it to the demodulated signal abnormality detecting unit 20a and the monitoring unit 21. The demodulated signal abnormality detecting unit 20a includes an optical-electrical converting unit 31, a branching unit 33a, a switching unit 34a, a plurality of detecting units 35-1 to 35-2, and a control unit 36a. The optical-electrical conversion unit 31 converts the optical signal converted by the electrical-optical conversion unit 17 into an electrical signal. The optical-electrical conversion unit 31 outputs the converted electrical signal to the demultiplexing unit 33a. The demultiplexing unit 33a demultiplexes the electrical signal output from the optical-electrical conversion unit 31 according to a frequency band. The demultiplexing unit 33a outputs the demultiplexed signal of a specific frequency band to the detection unit 35-1, and outputs signals of other frequency bands to the switching unit 34a. If the signal transmitting device 10 does not perform FM batch conversion, the demodulated signal abnormality detection unit 20a does not need to perform FM demodulation.

[0077] The signal transmission device 10 in the third embodiment may be configured as a signal transmission device including an electric signal branching unit 11, a pilot signal generating unit 12, a multiplexing unit 13, an electric signal abnormality detecting unit 14, an electric signal amplifying unit 15, an electric-optical converting unit 17, a demodulated signal abnormality detecting unit 20b, a monitoring unit 21, and an alarm processing unit 22. The electric signal amplifying unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the electric-optical converting unit 17. The electric-optical converting unit 17 converts the multiplexed signal amplified by the electric signal amplifying unit 15 into an optical signal and outputs it to the demodulated signal abnormality detecting unit 20b and the monitoring unit 21. The demodulated signal abnormality detecting unit 20b includes an optical-electrical converting unit 31, a branching unit 33, a switching unit 34b, a detecting unit 35, and a control unit 36b. The optical-electrical converting unit 31 converts the optical signal converted by the electric-optical converting unit 17 into an electric signal. The optical-electrical conversion unit 31 outputs the converted electrical signal to the demultiplexing unit 33. The demultiplexing unit 33 demultiplexes the electrical signal output from the optical-electrical conversion unit 31 according to frequency bands. The demultiplexing unit 33 outputs the demultiplexed signals of each frequency band to the switching unit 34b. If the signal transmitting device 10 does not perform FM batch conversion, the demodulated signal abnormality detection unit 20b does not need to perform FM demodulation.

[0078] The signal transmitting device 10 in the above-mentioned embodiment may be realized by a computer. In this case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. Note that the term "computer system" here includes hardware such as an OS (Operating System) and peripheral devices. Also, the term "computer-readable recording medium" refers to portable media such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), a CD-ROM, and a storage device such as a hard disk built into a computer system.

[0079] Furthermore, the term "computer-readable recording medium" may include a medium that dynamically holds a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such a case. The above program may be one for implementing part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system, or may be one that is realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0080] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0081] 10...signal transmission device, 11...electrical signal branching section, 12...pilot signal generating section, 13...multiplexing section, 14...electrical signal abnormality detection section, 15...electrical signal amplifier section, 16...FM batch conversion signal generating section, 17...electrical-optical conversion section, 18...optical signal amplifier section, 19...optical signal branching section, 20, 20a, 20b...demodulated signal abnormality detection section, 21...monitoring section, 22...alarm processing section, 31...optical-electrical conversion section, 32...demodulation section, 33, 33a...branching section, 34, 34a, 34b...switching section, 35, 35-1 to 35-2...detection section, 36, 36a, 36b...control section, 341, 341a, 341b...switch section, 342 to 344...input terminal, 345...connection section, 346~348…Output terminals

Claims

1. a pilot signal generating unit that generates pilot signals of a plurality of different frequencies as monitoring pilot signals used for detecting a level abnormality in a specific frequency band of an input signal; A branching unit that branches the pilot signals of the plurality of different frequencies; one or more detection units that detect at least two or more pilot signals of the plurality of pilot signals having different frequencies by using the signals demultiplexed by the demultiplexing unit; a switching unit that switches an output target so as to output each of the plurality of pilot signals of different frequencies branched by the branching unit to the one or more detection units at a predetermined period; a control unit that controls the switching unit so as to connect an output target of the switching unit to an output destination at the predetermined cycle; A signal transmitting device comprising:

2. The control unit controls the switching unit to connect the output target and the output destination of the switching unit at the predetermined cycle by synchronizing with a generation cycle of the pilot signal generated by the pilot signal generating unit.

2. A signal transmitting device according to claim 1.

3. a multiplexing unit that multiplexes an input signal with the pilot signals of the plurality of different frequencies generated by the pilot signal generating unit; a first conversion unit that converts the signal multiplexed by the multiplexing unit into an optical signal by optical modulation; a second conversion unit that converts the optical signal converted by the first conversion unit into an electrical signal; Further equipped with The branching unit branches the pilot signals of the plurality of different frequencies included in the electrical signal converted by the second conversion unit.

3. A signal transmitting device according to claim 1 or 2.

4. a multiplexing unit that multiplexes an input signal with the pilot signals of the plurality of different frequencies generated by the pilot signal generating unit; an FM batch conversion unit that performs FM (Frequency Modulation) batch conversion on the signals multiplexed by the multiplexing unit to generate an FM batch converted signal; a demodulation unit that demodulates the FM batch converted signal generated by the FM batch conversion unit; Further equipped with The branching unit branches the pilot signals of the plurality of different frequencies included in the FM batch converted signal demodulated by the demodulation unit.

3. A signal transmitting device according to claim 1 or 2.

5. the one or more detection units are a plurality of detection units, the branching unit is directly connected to some of the detection units among the plurality of detection units, and is connected to the remaining detection units among the plurality of detection units via the switching unit, and outputs some of the pilot signals obtained by branching the pilot signals of the plurality of different frequencies to the directly connected detection units, and outputs the remaining pilot signals obtained by branching the pilot signals of the plurality of different frequencies to the remaining detection units via the switching unit.

3. A signal transmitting device according to claim 1 or 2.

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