JP5008780B1 - Digital broadcast radio system - Google Patents

Abstract

To prevent wraparound of an FM signal from an FM retransmission slave station 3 when an antenna is shared by the loudspeaker slave station 2 and the FM retransmission slave station 3.
As shown in FIG. 2, an antenna 6 is shared by a loudspeaker slave station 2 and an FM retransmission slave station 3. As shown in FIG. 2, the FM retransmitting slave station 3 includes filters 30 and 31, an amplifier 32, a distributor 33, a digital receiver 34, a voice starter 35, and an FM transmitter 36. The filter 30, the amplifier 32, and the filter 31 are connected in series in this order, and the input side of the filter 30 is connected to the antenna 6. The output side of the filter 31 is connected to a distributor 33, one end on the output side of the distributor 33 is connected to the digital receiver 20 of the loudspeaker station 2, and the other end is connected to the digital receiver 34. . The filters 30 and 31 are filters that block the frequency band of the FM signal transmitted by the FM retransmission slave station 3.
[Selection] Figure 2

Description

  The present invention relates to a digital broadcast radio system having a loudspeaker slave station that communicates with a master station in a digital manner, and an FM retransmission slave station that converts the digital scheme into an FM scheme and retransmits it.

  In a conventional digital broadcast radio system, digitally modulated radio waves from the master station are received directly by a loudspeaker station installed on an outdoor pillar in each district or indirectly via a retransmitting slave station. Disaster prevention information etc. are informed to the residents of the surrounding houses through speakers.

  In addition, there may be a case where a separate receiver is installed in the house because it is difficult to hear sound in the house, or in a sparsely populated area, the construction cost per household of the loudspeaker station becomes high. In that case, there is a high probability that reception will be impossible due to shielding of a house, etc., and an outdoor antenna is installed to improve the reception environment.

  However, the cost required for improving the reception environment is higher than that of the individual receiver. In addition, it is difficult to predict the number of houses with poor reception environment, and the ratio of the number of houses with poor reception environment often exceeds 20%. It was often the case. In the case of the analog system, even in such a poor reception environment, it was possible to distinguish the noise mixed with the meaning from the surrounding context, but in the case of the digital system, the reception environment is bad Since the voice itself is interrupted, such a determination cannot be made, and improvement of the reception environment is essential.

  As a method for improving the reception environment at a low cost, retransmission by the FM method has been studied (Non-Patent Document 1). A receiver that receives separately digitally modulated radio waves and demodulates audio signals is provided near an outdoor loudspeaker station, and an FM transmitter that FM-modulates and outputs a carrier wave with the audio signals is provided in each home. By providing an FM receiver, the reception environment of the digital broadcast radio system can be improved at low cost. In addition, since a receiver is also provided on the FM retransmission side separately from the receiver on the loudspeaker station side, information is transmitted by voice output from an outdoor speaker near the loudspeaker station, and FM reception of each household under the loudspeaker station Information transmission by voice output from the machine can be performed independently.

Article published on the website of Toa Corporation, “60 MHz band analog FM re-transmission door-to-door reception system”, http://www.toa-inc.jp/70mhz/60mhztop.html (reference 2011-09-20)

  In the retransmission based on the FM scheme, a reception antenna is also required on the FM retransmission side in addition to the transmission / reception antenna on the loudspeaker station side, and a transmission antenna for transmitting an FM-modulated signal is also required. However, in the 60 MHz band used for disaster prevention radio, the antenna is physically large, and the transmission / reception antenna on the loudspeaker station side and the receiving antenna on the FM re-transmission side do not cause sneak or interference in the pillar where the loudspeaker station is installed It is difficult to attach two antennas.

  Further, since the FM modulated radio wave is close to the frequency of the digitally modulated radio wave from the master station, there is a problem that reception failure is caused by the wraparound of the FM modulated radio wave.

  Furthermore, since the digitally modulated radio wave from the master station cannot control the FM retransmission receiver or transmitter, there is a problem that the head of the audio signal is cut off or the volume cannot be controlled.

  Because of these problems, it has been difficult to put into practical use a method for improving the reception environment of a digital broadcast radio system by FM retransmission.

  Accordingly, an object of the present invention is to prevent interference between antennas and wraparound from an FM transmitter to a receiver on the side of a loudspeaker station in a digital broadcast radio system using FM retransmission. Another object is to prevent the sound output from the FM receiver from being cut off and to control the volume of the FM receiver.

According to a first aspect of the present invention, there is provided a loudspeaker station that receives a digital signal that is digitally modulated with an audio signal from a master station, demodulates the audio signal by a first receiver, and outputs sound to the surroundings by a speaker; The digital signal from the station is received, the audio signal is demodulated by the second receiver, the FM signal is FM-modulated by the FM transmitter, and the FM signal is generated. The FM signal is sent to the FM receiver installed in each home. In a digital broadcast radio system having an FM retransmission slave station for retransmission, an antenna for receiving a digital signal is shared by a loudspeaker slave station and an FM retransmission slave station, and the digital signal from the antenna is input. A filter that cuts off the frequency band of the FM signal, and a digital signal from the filter is divided into two, one being output to the first receiver of the loudspeaker slave station and the other being output to the second receiver of the FM retransmission slave station With a distributor to Have a second receiver has a ramp which audio signals from the master station is turned on and off depending on whether it is emergency information, FM transmitter senses the presence or absence of lighting of the lamp, that A control signal for controlling the volume output from the FM receiver is generated based on the presence / absence, and an FM signal is generated by FM modulation with the control signal, and the FM receiver controls the volume based on the control signal. Is a digital broadcast radio system.

  In order to compensate for the distribution loss due to the distributor, it is desirable to provide an amplifier in front of or behind the distributor. The filter and the distributor may be incorporated in the loudspeaker slave station, may be incorporated in the FM retransmission slave station, or may be provided separately from them.

  In a second aspect based on the first aspect, the FM retransmission slave station has a voice starter that is connected to the second receiver and controls the start of the FM transmitter. A digital signal that is digitally modulated with a broadcast start signal is transmitted and received by the second receiver, and the FM transmitter is activated based on a click sound generated when the broadcast start signal is demodulated and output. Is a digital broadcast radio system.

According to a third aspect , in the second aspect, the FM transmitter has transmission means for cutting the voice signal having a frequency lower than a predetermined frequency, and then FM-modulating the carrier wave with the voice signal and transmitting the second signal. Receives a digital signal digitally modulated with a test broadcast signal having a frequency lower than a predetermined frequency from the master station, demodulates the test broadcast signal, and outputs the demodulated signal to the voice starter. The voice starter receives the test broadcast signal as input. Then, the FM transmitter is started, and the FM transmitter cuts the test broadcast signal by the transmission means and transmits only the carrier wave. The FM receiver confirms the operation of the FM receiver according to the reception state of the carrier wave from the FM transmitter in the FM receiver. A digital broadcast radio system characterized by The predetermined frequency is, for example, 300 Hz.

According to the present invention, even when the receiving antenna is shared by the loudspeaker slave station and the FM retransmission slave station, the FM signal from the FM retransmission slave station wraps around and suppresses the occurrence of reception failure. be able to.
Also, according to the present invention , the volume of the FM receiver can be controlled even in a system that performs FM modulation and retransmits.

  Further, according to the second invention, it is possible to prevent the head of the audio of the audio broadcast.

Further, according to the third invention , it is possible to check the operation of the FM receiver without outputting sound from the FM receiver.

The figure which showed the structure of the digital broadcast radio | wireless system of Example 1. FIG. The figure which showed the structure of the expansion child station 2 and FM re-transmission slave station 3. FIG.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a diagram illustrating a configuration of a digital broadcast radio system according to the first embodiment. As shown in FIG. 1, the digital broadcast radio system includes a master station 1, a loudspeaker slave station 2, an FM retransmission slave station 3, and an FM receiver 4.

  The master station 1 digitally modulates the carrier wave with a broadcast start signal notifying the start of audio broadcast such as disaster prevention information, an audio signal of audio broadcast, a control signal for controlling the operation of the loudspeaker slave station 2 and the like. Transmit to a plurality of loudspeaker slave stations 2. The frequency of the broadcast signal is 60 MHz, and the modulation method is, for example, 16QAM. The master station 1 is installed at a disaster prevention center in a municipality, for example.

  As shown in FIG. 1, the loudspeaker slave station 2 is attached to a pole 5 such as a telephone pole or a telephone pole, and the digital signal received from the antenna 6 attached to the pole 5 is input. The antenna 6 is, for example, a Yagi antenna with directivity directed toward the master station 1 side. The loudspeaker slave station 2 demodulates the audio signal from the received digital signal and outputs the sound to the surroundings from the speaker 7 attached to the pillar 5 based on the audio signal. The loudspeaker slave station 2 digitally modulates a status signal, which is information indicating its own operation status, and transmits the modulated radio wave from the antenna 6 to the master station 1.

  FIG. 2 is a diagram showing the configuration of the loudspeaker slave station 2 and the FM retransmission slave station 3. The loudspeaker slave station 2 includes a digital receiver 20, a digital transmitter 21, and a switch 22. The connection between the antenna 6 and the digital receiver 20 and the connection between the antenna 6 and the digital transmitter 21 are dynamically switched by a switch 22. Further, the FM receiver 3 is connected between the switch 22 and the digital receiver 20. The audio output side of the digital receiver 20 is connected to the speaker 7. The digital receiver 20 demodulates a broadcast start signal, a control signal, and an audio signal from the received digital signal, and outputs an audio signal based on the control signal. The digital transmitter 21 digitally modulates the carrier wave with a status signal that is information indicating the operation status of the loudspeaker slave station 2 and transmits the result to the master station 1 from the antenna 6. The digital transmitter 21 not only transmits a status signal, but also connects a weather observation device such as a rain gauge and an anemometer to the digital transmitter 21, and connects the switch 22 to the digital transmitter 21 side as needed. The weather observation data may be transmitted to the master station 1 at any time.

  As shown in FIG. 1, the FM retransmission slave station 3 is attached to the pillar 5 adjacent to the loudspeaker slave station 2. The FM retransmission substation 3 converts the digitally modulated radio wave received from the antenna 6 from the master station 1 into an FM modulated radio wave, and retransmits it using the antenna 8 attached to the pillar 5.

  Further, as shown in FIG. 2, the FM retransmission sub-station 3 includes filters 30 and 31, an amplifier 32, a distributor 33, a digital receiver 34, a voice starter 35, an FM transmitter 36, a power supply unit 37, and a battery 38. , Is composed of. The filter 30, the amplifier 32, and the filter 31 are connected in series in this order, and the input side of the filter 30 is inserted between the switch 22 of the loudspeaker station 2 and the digital receiver 20. The output side of the filter 31 is connected to a distributor 33, one end on the output side of the distributor 33 is connected to the digital receiver 20 of the loudspeaker station 2, and the other end is connected to the digital receiver 34. . The filters 30 and 31 are filters that transmit the band of 59.0 to 65.5 MHz and block the band of 68.0 to 69.0 MHz, which is the frequency band of the FM signal transmitted by the FM retransmission slave station 3. For example, it is configured by a combination of a band pass filter and a notch filter.

  As the digital receiver 34, a digital receiver provided in a conventional digital broadcast radio system can be used. The digital receiver 34 demodulates a broadcast start signal, a control signal, and an audio signal from the received digital signal, and outputs an audio signal based on the control signal. The digital receiver 34 has an LED lamp 340. When the audio signal from the master station 1 is emergency information, the LED lamp 340 is lit. The audio signal output side of the digital receiver 34 is connected to the audio activation machine 35. The output side of the voice starter 35 is connected to the FM transmitter 36.

  The FM transmitter 36 has means for detecting whether or not the LED lamp 340 is lit by a photodiode or the like. In addition, the FM transmitter 36 receives a sound signal from the digital receiver 34 via the sound starter 35. The FM transmitter 36 performs FM modulation on the carrier wave with the control signal and the audio signal, and outputs an FM signal. The frequency of the FM signal is 65.000 to 68.9875 MHz, and the frequency of the control signal and the audio signal is 300 to 3400 Hz.

  The amplifier 32, the digital receiver 34, and the FM transmitter 36 are driven by being supplied with power by a power supply 37 connected to a commercial power source. Further, a battery 38 is provided for supplying power to the amplifier 32, the digital receiver 34, and the FM transmitter 36 via the power supply 37 during a power failure of the commercial power supply.

  In the first embodiment, the filters 30, 31, the amplifier 32, and the distributor 33 are provided on the FM retransmission slave station 3 side, but may be provided on the loudspeaker slave station 2 side, and further FM retransmission. The slave station 3 and the loudspeaker slave station 2 may be provided independently.

  The FM receiver 4 is arranged in the house 9 of each household, receives the FM signal subjected to FM modulation from the antenna 8, demodulates the control signal and the sound signal, and outputs sound based on the control signal. .

  Next, the operation of the digital broadcast radio system according to the first embodiment will be described in more detail.

  The master station 1 first digitally modulates the carrier wave with a broadcast start signal that informs the start of the audio broadcast and transmits a digital signal, and then digitally modulates the carrier wave with an audio signal and a control signal for the audio broadcast. Finally, the carrier wave is digitally modulated with a broadcast end signal notifying the end of the audio broadcast, and a digital signal is transmitted. The control signal includes a unique identification number of the digital receiver 20 of the loudspeaker slave station 2 and the digital receiver 34 of the FM repeater slave station 3 that determines which loudspeaker slave station 2 and FM retransmission slave station 3 perform audio broadcasting. Contains information. A digital signal is 60 MHz, for example, and is a frequency used for disaster prevention administrative radio. The control signal has a frequency of less than 300 Hz (for example, 280 Hz), and the broadcast start signal, broadcast end signal, and audio signal are 300 Hz to 3400 Hz.

  The digital signal from the master station 1 is received by the antenna 6 and input to the FM retransmission slave station 3 when the switch 22 is connected to the FM retransmission slave station 3 side.

  The digital signal input to the FM retransmission slave station 3 passes through the filters 30 and 31, is amplified by the amplifier 32, and is then divided into two by the distributor 33, and one is sent to the digital receiver 20 of the loudspeaker slave station 2. The other is input to the digital receiver 34 of the FM retransmission slave station 3. The amplifier 32 is for recovering the loss due to the two distributions. The role of the filters 30 and 31 will be described later.

  In the digital receiver 20 of the loudspeaker slave station 2, the digital receiver 20 itself is driven by receiving the broadcast start signal, receives the digital signal that arrives thereafter, and demodulates the audio signal and the control signal from the digital signal. Then, the unique identification number specified by the control signal is compared with its own unique identification number, and when the own unique identification number is included, the sound signal is output to the speaker 7 to amplify the sound broadcasting. Tell the slave station 2 around. If it does not include its own unique identification number, no audio signal is output to the speaker 7 and audio broadcasting is not performed. Further, the volume of the audio broadcast is controlled based on the control signal. After the audio broadcast, when the digital receiver 20 receives the broadcast end signal, it stops driving itself and ends the audio broadcast.

  Similarly, in the digital receiver 34 of the FM retransmission substation 3, the digital receiver 20 itself is driven by receiving the broadcast start signal, receives the digital signal that arrives thereafter, and demodulates the audio signal and the control signal from the digital signal. To do. Then, the unique identification number designated by the control signal is compared with its own unique identification number, and if its own unique identification number is included, the voice signal is output to the voice activation machine 35, If the unique identification number is not included, no voice signal is output to the voice activation machine 35. Here, when a broadcast start signal is input to the digital receiver 34, a click sound is output. Further, when the control signal includes information indicating emergency broadcast, the LED lamp 340 of the digital receiver 34 is turned on. The digital receiver 34 outputs not only the audio signal of 300 to 3400 Hz but also the control signal of less than 300 Hz.

  The voice starter 35 drives the FM transmitter 36 when a click sound is input. Then, the audio signal from the digital receiver 34 is received via the audio starter 35. As described above, since the audio signal is input to the FM transmitter 36 after the FM transmitter 36 is first driven by the click sound, it is possible to prevent the audio broadcast from being cut off. Further, after the audio broadcast, when the digital receiver 34 receives the broadcast end signal, the digital receiver 34 similarly outputs a click sound and is input to the audio starter 35. When the second click sound is input, driving of the FM transmitter 36 is stopped and the audio broadcasting is ended.

  The FM transmitter 36 detects whether the LED lamp 340 is lit by a photodiode or the like. When the LED lamp 340 is lit, a control signal that forcibly maximizes the volume of the FM receiver 4 is generated. Also, a control signal including information on the unique identification number of the FM transmitter 36 itself is generated. Then, the carrier wave is FM-modulated with these control signals and the audio signal from the digital receiver 34 and transmitted from the antenna 8 to the FM receiver 4 under the control. In addition, when the LED lamp 340 is not lit, a signal for controlling the volume is not generated, and after the audio signal is amplified to a specified level, the control signal includes information on the unique identification number of the FM transmitter 36 itself. The carrier wave is FM-modulated with the sound signal and transmitted to the FM receiver 4. The FM transmitter 36 also receives a control signal of less than 300 Hz from the digital receiver 34 via the voice starter 35, but this signal is cut so that the carrier wave is not FM-modulated. A signal less than 300 Hz is cut using, for example, a filter. The frequency of the carrier wave is, for example, 68.0 to 69.0 MHz, and is set so as not to overlap with the frequency of the adjacent area. The control signal is 300 to 3400 Hz, which is the same as the audio signal.

  Here, the FM signal transmitted from the antenna 8 may wrap around and be received by the antenna 6. Even in this case, since the filters 30 and 31 block the frequency of 68.0 to 69.0 MHz, which is the frequency band of the FM signal, the digital receiver 20 of the loudspeaker slave station 2 and the FM retransmission slave station 3 An FM signal is not input to the digital receiver 34, and a reception failure can be prevented.

  The FM receiver 4 receives the FM signal from the FM retransmission slave station 3 and demodulates the control signal and the audio signal. From the unique identification number of the FM transmitter 36 of the FM retransmission slave station 3 included in the control signal, it is determined whether or not it is the subordinate FM receiver 4, and if it is subordinate, the audio signal Audio broadcast is output based on the above, and no audio is output if it is not under its control. Further, when the control signal includes that the volume is maximized, audio broadcasting is performed at the maximum volume regardless of the volume volume setting of the FM receiver 4. Thereby, the emergency broadcast can always be broadcast at the maximum volume. If the control signal does not include volume control information, audio broadcasting is performed according to the volume volume setting of the FM receiver 4. Since the frequency of the carrier wave is changed from the adjacent area, the FM signal for the adjacent area is never received. Even if FM signals having the same frequency for other areas that are not adjacent to each other are received, since the control signal is used for identification as described above, audio broadcasts for other areas having the same frequency are mixed and output. There is nothing.

  As described above, in the digital broadcast radio system according to the first embodiment, the loudspeaker slave station 2 and the FM retransmission slave station 3 share the antenna 6, and therefore, when two antennas are provided independently without being shared. Thus, the problem of causing mutual interference between antennas does not occur. Further, the filters 30 and 31 are provided to block the FM retransmission frequency band, and the distributor 33 is provided to return one to the digital receiver 20 on the loudspeaker station 2 side. It is possible to prevent a reception failure from occurring due to wraparound.

  In addition, the click sound output when the broadcast start signal for starting the digital receiver 34 is input to the digital receiver 34 is detected by the sound starter 35, and the sound broadcast reaches the FM transmitter 36. The FM transmitter 36 can be activated before. Therefore, it is possible to prevent the audio broadcast from being cut off. Further, the FM transmitter 36 can generate a control signal for controlling the sound volume by detecting whether or not the LED lamp 340 of the digital receiver 34 is turned on by the FM transmitter 36, and the FM receiver 4 outputs the control signal. Voice control can be performed.

  Next, a method for confirming the operation of the FM receiver 4 in the digital broadcast radio system according to the first embodiment will be described.

  Conventionally, in order to confirm the operation of the FM receiver 4, a test broadcast is actually performed to generate sound, or a scheduled announcement broadcast is waited for and the announcement broadcast is used. Since the FM retransmission slave station 3 is arranged in a large number of areas, the frequency of the FM signal output from the FM transmitter 36 is the same as the frequency of the FM signal output from the FM transmitter 36 in another area that is not adjacent. May be the same. Therefore, in confirming the operation of the FM receiver 4, it is necessary to confirm not only the reception level but also the interference state of the same frequency. Therefore, it is necessary to perform test broadcasting for all areas. However, in the conventional method of performing test broadcasting, sound is generated in all areas for use in confirming the operation, and this becomes a kind of complaint from residents in unrelated areas. In addition, the method of using the scheduled announcement broadcast has a problem in that there are restrictions on the time period during which the operation is confirmed. However, if the following method is executed using the digital broadcast wireless system of the first embodiment, such a problem can be solved.

  First, the master station 1 digitally modulates a carrier wave with a signal of less than 300 Hz, specifically, for example, 280 Hz as a test broadcast signal, and transmits a digital signal. The test broadcast signal includes information on a unique identification number for designating the digital receiver 34 in the area where the test broadcast is desired. The digital signal is input to the digital receiver 34, and the digital receiver 34 that matches the unique identification number included in the test broadcast signal demodulates the test broadcast signal and outputs the demodulated signal to the voice starter 35. The test broadcast signal is also input to the digital receiver 20 via the distributor 33. However, since the test broadcast signal does not include a unique identification number for designating the digital receiver 20, the digital receiver No test broadcast signal is output from 20.

  The voice starter 35 starts the FM transmitter 36 when a test broadcast signal is input. The FM transmitter 36 cuts a signal of less than 300 Hz and FM modulates the carrier wave and transmits it. Therefore, the test broadcast signal is cut and only the carrier wave is transmitted. The FM receiver 4 receives the carrier wave from the FM transmitter 36 and confirms the reception level and the interference state. Since only the carrier wave is received, no sound is output from the FM receiver 4. If the operation of the FM receiver 4 is confirmed by such a method, there is no restriction on the operation confirmation time zone, and no complaints about sound occur.

  In the digital broadcast radio system according to the first embodiment, the loudspeaker slave station 2 and the FM retransmission slave station 3 are installed on the pillar 5, but may be installed at a high place in a building or a house. In the first embodiment, the direct communication between the master station 1 and the loudspeaker slave station 2 is performed. However, a retransmission slave station and a relay station are provided, and the master station 1 and the repeater slave station and the relay station are connected via the retransmission slave station and the relay station. A configuration may be employed in which the loudspeaker slave station 2 communicates indirectly.

  The digital broadcast radio system of the present invention can be used for digital disaster prevention administrative radio and the like.

1: Master station 2: Loudspeaker slave station 3: FM retransmission slave station 4: FM receiver 5: Pillar 6, 8: Antenna 7: Speaker 9: House 20, 34: Receiver 21: Transmitter 22: Switch 30, 31: Filter 32: Amplifier 33: Distributor 35: Voice starter 36: FM transmitter

Claims (3)

A loudspeaker station that receives a digital signal digitally modulated with a voice signal from a master station, demodulates the voice signal by a first receiver, and outputs a voice to the surroundings by a speaker; and the digital signal from the master station The signal is received, the audio signal is demodulated by a second receiver, the FM signal is FM-modulated by an FM transmitter to generate an FM signal, and the FM signal is re-transmitted to the FM receiver installed in each home. In a digital broadcast radio system having an FM retransmission slave station for transmission,
An antenna for receiving the digital signal is shared by the loudspeaker slave station and the FM retransmission slave station,
The digital signal from the antenna is inputted and a filter that cuts off the frequency band of the FM signal, and the digital signal from the filter is divided into two, one to the first receiver of the loudspeaker station and the other to the FM a divider for outputting to the second receiver retransmission slave station, was closed,
The second receiver has a lamp that is turned on / off depending on whether the audio signal from the master station is emergency information,
The FM transmitter senses whether the lamp is lit, generates a control signal for controlling the volume output from the FM receiver based on the presence of the lamp, and generates an FM signal by performing FM modulation with the control signal. And
The FM receiver controls the volume based on the control signal;
A digital broadcast radio system characterized by this. The FM retransmission slave station has a voice starter that is connected to the second receiver and controls the start of the FM transmitter;
The voice starter is based on a click sound generated when a digital signal digitally modulated with a broadcast start signal is transmitted from the master station and received by the second receiver, and the broadcast start signal is demodulated and output. , Activate the FM transmitter,
The digital broadcast radio system according to claim 1. The FM transmitter has a transmission unit that cuts the audio signal having a frequency lower than a predetermined frequency and then performs FM modulation on the carrier wave with the audio signal and transmits the carrier wave;
The second receiver receives a digital signal digitally modulated with a test broadcast signal having a frequency lower than the predetermined frequency from a master station, demodulates the test broadcast signal, and outputs the demodulated signal to the voice activation unit.
The voice activation machine activates the FM transmitter based on the input of the test broadcast signal,
The FM transmitter transmits only a carrier wave by cutting the test broadcast signal by the transmission means,
The operation of the FM receiver is confirmed according to the reception state of the carrier wave from the FM transmitter in the FM receiver.
The digital broadcast radio system according to claim 2.

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