JP4189352B2 - Infrared communication device - Google Patents

Description

  The present invention relates to an infrared communication device, and particularly includes, for example, an assigning unit that assigns one of a plurality of prepared channels to a counterpart device, and the infrared signal converted based on the channel assigned by the assigning unit The present invention relates to an infrared communication device that transmits and receives data to and from a counterpart device.

  As this type of infrared communication device, there is one conventionally applied to an infrared conference system (model: ATCS-50) disclosed in Non-Patent Document 1, for example. This infrared conference system includes a master control unit (model: ATCS-C50) as a main device, and a multi-channel light emitting / receiving unit (model: ATCS-A50) as a relay device that constitutes an infrared communication device together with the master control unit. And a plurality of conference microphone units (model: ATCS-M50) as terminal devices. Among these, the master control unit is installed in the corner of the conference room, for example, and the multi-channel light emitting / receiving unit is mounted on the ceiling of the conference room, for example. Each conference microphone unit is arranged at an appropriate location in the conference room.

  In such a configuration, when an utterance is made by any conference microphone unit, the utterance content (voice) is reproduced (monitored) on the master control unit side and all the conference microphone unit sides including the utterance source. In order to realize this, an FM (Frequency Modulation) signal including the content of the message is transmitted / received between the master control unit and each conference microphone unit via the multi-channel light emitting / receiving unit. Specifically, the FM signal is transmitted and received between the master control unit and the multi-channel light emitting / receiving unit via a coaxial cable, that is, wired. The FM signal is transmitted / received between the multi-channel light emitting / receiving unit and each conference microphone unit using infrared as a communication medium, that is, converted into an infrared signal (luminance modulation). In the infrared conference system disclosed in Non-Patent Document 1, four communication channels are prepared. That is, it is possible to speak at the same time using up to four conference microphone units. Which conference microphone unit uses which channel is automatically assigned by the master control unit in response to an individual speech request from each conference microphone unit.

  As a communication device using infrared as a medium, for example, there is a wireless microphone system disclosed in Non-Patent Document 2. This wireless microphone system includes, for example, a hand-type optical wireless microphone (model; WM-PH711 to PH714) as a transmitter, a light receiving sensor (model; WT-PS31 to PS32) as a relay device, and a light as a receiver. And a wireless tuner (model: WT-PH31 to PH32). The light receiving sensor is attached to the ceiling of the conference room, for example, and the optical wireless tuner is installed in the corner of the conference room, for example.

According to this configuration, the sound input to the optical wireless microphone is converted into an audio signal. An FM signal is generated based on the audio signal, and the FM signal is converted into an infrared signal and emitted from the optical wireless microphone 6. The emitted infrared signal enters the light receiving sensor, where it is converted into an electrical signal, that is, an FM signal. The FM signal is input to the wireless tuner via a coaxial cable, and is demodulated here. As a result, the audio signal is reproduced, and the reproduced audio signal is input to the speaker through the amplifier or the mixer, and is output as sound from the speaker.
Audio Technica Inc. IR Conference System “ATCS-50” Product Description, [online], [Search May 20, 2004], Internet <URL; http://www.audio-technica.co.jp /proaudio/infrared/atcs-50/ATCS-50.html> “Victory Wireless Microphone System WT-PH31 Series” catalog made by JVC, [online], [Search May 20, 2004], Internet <URL; http://www.jvc-victor.co.jp/ pdf / pro / catalog / wt-ph31.pdf>

  However, when the infrared conference system disclosed in Non-Patent Document 1 and the wireless microphone system disclosed in Non-Patent Document 2 are used at the same time (conference room), for example, interference occurs between the two. And communication interference such as intermodulation products may occur. In particular, in an infrared conference system, the channel used by each conference microphone unit is automatically assigned by the master control unit as described above. In other words, it is undefined which channel is used by which conference microphone unit. For this reason, the infrared conference system as a whole causes communication interference with the wireless microphone system. That is, there is a problem that the infrared conference system disclosed in Non-Patent Document 1 and the wireless microphone system disclosed in Non-Patent Document 2 cannot be used at the same place at the same time.

  Therefore, an object of the present invention is to provide an infrared communication device that can be used simultaneously in the same place as other systems using infrared as a communication medium.

The present invention includes a plurality of terminal devices, a light transmitting / receiving device, and a center device. Any of the terminal devices converts an uplink control data including an identification number representing the terminal device operated by the speech request switch into a first uplink FM signal by operating a speech request switch included in the terminal device. One upstream FM signal is converted into a first upstream infrared signal by a first light transmitting means provided in the terminal device, and then emitted. The light transmitting / receiving device converts the first upstream infrared signal into a first upstream FM signal by the first light receiving means, and transmits the first upstream FM signal to the center device. The center device demodulates the first uplink FM signal from the light transmitting / receiving device, reproduces the uplink control data, analyzes the uplink control data, makes a request for speech, and the requesting terminal device And when it is possible to speak, it generates downlink control data that includes an identification number representing the requesting terminal device and permits the requesting terminal device to speak, and converts this downlink control data into a first downlink FM signal To the light transmitting / receiving device. The light transmitting / receiving device converts the transmitted first downstream FM signal into a first downstream infrared signal by a second light transmitting means included in the light transmitting / receiving device, and emits it. Each terminal device converts the first downstream infrared signal into the first downstream FM signal by the second light receiving means provided therein, reproduces the downstream control data, and sends it to itself from the identification number included therein. Judge what has been done. The terminal device, to which downlink control data is sent, converts the audio signal into a second uplink FM signal, and the second uplink FM signal is converted into a second infrared uplink signal by the first light transmitting means. Convert to fire. The light transmitting / receiving device is a first light receiving means for converting a second infrared upstream signal into a second upstream FM signal and transmitting it to the center device. The center device has second uplink FM signal receiving means for converting the second uplink FM signal into an audio signal. The center apparatus has a table in which a channel already allocated and a channel whose allocation is prohibited among a plurality of high-frequency channels for the second uplink FM signal are written, and it is recognized that the speech request has been made. At this time, an empty channel is searched for among the high-frequency channels based on the table, and if there is an empty channel, the downlink control data includes information indicating the empty channel. The terminal device permitted to speak generates a second uplink FM signal of a high-frequency channel based on information indicating an empty channel included in the downlink control data. The center device has an assignment prohibition switch for writing a high-frequency channel that causes interference or intermodulation product with the frequency band of another communication device when used at the same time as the assignment-prohibited channel in the table.

In the present invention, the center device may have the same number of second uplink FM signal receiving means as the high-frequency channel. In this case, the center device synthesizes the audio signals from these receiving means and converts them into a second downlink FM signal of a high frequency channel different from each of the high frequency channels, and the second transmission / reception of the light transmitting / receiving device. Means for transmitting to the means. The second light receiving means of the light transmitting / receiving device converts the second downstream FM signal into a second downstream infrared signal and emits it to each terminal device. Each of the terminal devices converts a second downstream infrared signal into a second downstream FM signal by a second light receiving unit, and converts a second downstream FM signal into a voice signal. have. The center device includes invalidating means for manually invalidating the receiving means.

Alternatively, in the present invention, the center device can have the same number of second uplink FM signal receiving means as the high-frequency channel. In this case, the center device synthesizes the audio signals from these receiving means and converts them into a second downlink FM signal of a high frequency channel different from each of the high frequency channels, and the second light transmission of the light transmitting / receiving device. Means for transmitting to the means. The second light transmitting means of the light transmitting / receiving device converts the second downstream FM signal into a second downstream infrared signal and emits it to each terminal device. Each of the terminal devices converts a second downstream infrared signal into a second downstream FM signal by a second light receiving unit, and converts a second downstream FM signal into a voice signal. have. The center apparatus determines whether each of the second uplink FM signal receiving means has received a corresponding second uplink FM signal, and determines the second uplink FM signal by the determining means. Invalidating means for invalidating the receiving means determined to be non-received.

  According to the present invention, by setting a channel that may cause communication interference with another system as an assignment-prohibited channel, the occurrence of the communication interference can be prevented. That is, it can be used simultaneously in the same place as other systems without causing the communication interruption.

  A first embodiment of the present invention will be described with reference to FIGS.

  In the first embodiment, the present invention is applied to an infrared conference system 10 as shown in FIG. 1, and the infrared conference system 10 includes one center device 12 as a main device and the center device 1. And a plurality of transmission / reception devices 14, 14,... As relay devices constituting the infrared communication device, and a plurality of terminal devices 18, 18,. Among these, the center apparatus 12 is installed in the corner of a meeting room, for example, and each light transmission / reception apparatus 14,14, ... is attached to the ceiling or wall surface of the meeting room. The center device 12 and the light transmitting / receiving devices 14, 14,... Are connected to each other by a coaxial cable 20. In FIG. 1, for convenience of explanation, the center device 12 and each light transmitting / receiving device 14, 14,... Are connected by a single coaxial cable 20. 20 or via a mixing distributor (not shown). And each terminal device 18, 18, ... is arrange | positioned on the appropriate location of the conference room, for example, on the table for each speaker. These terminal devices 18, 18,... Are assigned individual identification numbers. As will be described later, in the conference room, an infrared microphone system 30 as another system may be used at the same time.

  Here, the overall operation of the infrared conference system 10 will be briefly described. For example, it is assumed that a request for speech is made by a certain terminal device 18 now. This speech request is made by operating a speech request switch on an operation panel (not shown) provided in the terminal device 18. Then, in the terminal device 18, uplink control data indicating that a speech request has been made is generated. In this uplink control data, an identification number representing the origin of the request for speech is also incorporated. The uplink control data is converted (frequency modulated) into an uplink FM signal, and the uplink FM signal is converted (infrared modulation) into an infrared signal having a wavelength of 870 [nm]. Fired. In order to emit this infrared signal, the terminal device 18 includes a light transmitting means (not shown) such as an infrared light emitting diode (LED).

  The upstream infrared signal emitted from the terminal device 18 enters the light transmitting / receiving device 14 in an appropriate place, for example, in the vicinity of the terminal device 18. The light transmitting / receiving device 14 includes light receiving means (not shown) such as a photodiode (PD) for converting an incident infrared signal into an electric signal. The electrical signal converted by the photodiode, that is, the upstream FM signal is sent to the center device 12 via the coaxial cable 20 or in addition to the above-described mixing / distributing device.

  The center device 12 receives the uplink FM signal transmitted from the light transmitting / receiving device 14, converts the received uplink FM signal into an intermediate frequency signal, and further performs demodulation processing on the intermediate frequency signal. Thereby, the uplink control data is reproduced. Further, the center device 12 analyzes the reproduced uplink control data, and recognizes that the speech request has been made this time and the terminal device 18 that is the request source. Then, downlink control data indicating that the terminal device 18 is allowed to speak is generated, and the downlink control data is converted into a downlink FM signal having a reference frequency (frequency band) different from that of the uplink FM signal. This downstream FM signal is sent to all the light transmitting / receiving devices 14, 14,... Via the coaxial cable 20 or in addition to the above-mentioned mixing / distributing device.

  Each of the light transmitting / receiving devices 14, 14,... Includes a light transmitting means (not shown), for example, an infrared light emitting diode, and causes the infrared light emitting diode to emit light in accordance with a downstream FM signal sent from the center device 12. Accordingly, an infrared signal having a wavelength of 870 [nm] is emitted from each of the light transmitting / receiving devices 14, 14,... (Infrared light emitting diode).

  The downstream infrared signal emitted from each light transmitting / receiving device 14, 14,... Is appropriately incident on each terminal device 18, 18,. Each terminal device 18 includes light receiving means (not shown) such as a photodiode for converting an incident infrared signal into an electric signal. The electrical signal converted by the photodiode, that is, the downstream FM signal is converted into an intermediate frequency signal, and the intermediate frequency signal is further subjected to demodulation processing. Thereby, the downlink control data is reproduced. The terminal device 18 determines whether or not the reproduced downlink control data has been sent to itself, for example, whether or not its own identification number is incorporated in the downlink control data. Here, only the terminal device 18 that has received the downlink control data sent to itself is permitted to speak, that is, can speak.

  When a speech is made by the terminal device 18, that is, when a voice is input to the microphone 16 of the terminal device 18, the voice is converted into a voice signal, and an uplink FM signal is generated again based on the voice signal. Is done. Note that the reference frequency of the uplink FM signal is designated by the downlink control data, and so to speak is assigned. Then, the generated uplink FM signal is converted into an infrared signal and emitted from the terminal device 18 in the same manner as described above.

  The upstream infrared signal emitted from the terminal device 18 is incident on the light transmitting / receiving device 14 in the vicinity of the terminal device 18 as described above. The infrared signal incident on the light transmitting / receiving device 14 is converted into an upstream FM signal by the above-described photodiode (strictly including a tuning circuit), and the converted upstream FM signal is transmitted to the center device 12.

  The center device 12 receives the upstream FM signal sent from the light transmitting / receiving device 14, converts the received upstream FM signal into an intermediate frequency signal, further performs demodulation processing on the intermediate frequency signal, and reproduces an audio signal To do. The reproduced audio signal is input to an external speaker (not shown) connected to an external output terminal (not shown) of the center device 12. Thereby, the voice of the utterance is reproduced from the external speaker. Furthermore, the center device 12 generates a downlink FM signal again based on the reproduced audio signal. This downstream FM signal is sent to each of the light transmitting / receiving devices 14, 14,.

  Each of the light transmitting / receiving devices 14, 14,... Causes the above-described infrared light emitting diodes to emit light in accordance with the downlink FM signal sent from the center device 12. As a result, an infrared signal is emitted from each of the light transmitting / receiving devices 14, 14,... (Infrared light emitting diode), and this downstream infrared signal is incident on each terminal device 18, 18,.

  Infrared signals incident on the respective terminal devices 18 are converted into downlink FM signals by the above-described photodiodes (strictly including a tuning circuit). The downstream FM signal is converted into an intermediate frequency signal, and further demodulated. As a result, the audio signal is reproduced, and the reproduced audio signal is input to a monitor speaker (not shown) provided on the operation panel. As a result, in all the terminal devices 14, 14,..., The voice of the utterance is reproduced and, in other words, monitored.

  In this embodiment, a maximum of four terminal devices 18, 18,... Can speak at the same time. In other words, four channels are prepared as so-called uplink channels from the terminal devices 18, 18,... To the center device 12 through the light transmitting / receiving devices 14, 14,. Specifically, as shown in FIG. 2, four channels of CH1, CH2, CH3, and CH4 are prepared as the uplink channel, and each reference frequency (carrier frequency) is 7.35 [MHz. ], 8.10 [MHz], 8.55 [MHz], and 9.15 [MHz]. Which of the uplink channels CH1, CH2, CH3, and CH4 is assigned to which terminal device 18 is automatically controlled by the center device 12 in response to a request for speech from the individual terminal device 18.

  Further, the uplink control data described above is transmitted via the uplink channels CH1, CH2, CH3, and CH4 while being mixed with the uplink audio signal. In particular, uplink control data including a speech request is transmitted via a specific channel, for example, CH1. At this time, the uplink control data is superimposed on the audio signal by a subcarrier signal (subcarrier) having a frequency of 24 [kHz]. For example, an FSK (Frequency Shift Keying) method is employed as the modulation method of the uplink control data.

  On the other hand, two channels are prepared as downlink channels from the center device 12 to the terminal devices 18, 18,... Via the light transmitting / receiving devices 14, 14,. Specifically, as shown in FIG. 2, a channel CH1 having a reference frequency of 1.95 [MHz] and a channel CH2 having a reference frequency of 2.25 [MHz] are prepared. Of these, the channel CH1 is a channel for main audio, and the channel CH2 is a channel for sub audio. Normally, the main audio channel CH1 is preferentially used, and the above-described monitoring audio signal is transmitted through the main audio channel CH1. On the other hand, the secondary audio channel CH2 is used, for example, when transmitting simultaneous interpretation sound. This simultaneous interpretation sound is input from, for example, an external microphone (not shown) connected to an external input terminal (not shown) of the center device 12. Note that the above-described operation panel of each terminal device 18 is provided with a channel selection switch (not shown) for arbitrarily selecting one of the main audio channel CH1 and the sub audio channel CH2. Only the sound of the channel CH1 or CH2 (monitoring sound or simultaneous interpretation sound) selected by the above is reproduced on the terminal device 18 side.

  Each of the downlink channels CH1 and CH2 is also used as a so-called control channel for transmitting downlink control data, like each of the uplink channels CH1, CH2, CH3, and CH4. That is, the downlink control data is also superposed on the downlink audio signal after being subjected to FSK processing by a subcarrier signal (subcarrier) having a frequency of 24 [kHz]. And it is transmitted to each terminal device 14, 14,... Via each downlink channel CH1 and CH2 while being superimposed on this downlink audio signal.

  As described above, in the conference room where the infrared conference system 10 is installed, the infrared microphone system 30 as another system may be used at the same time. This infrared microphone system 30 is used, for example, when giving a presentation. The infrared microphone system 30 is basically the same as the wireless microphone system disclosed in Non-Patent Document 2 described above, and specifically, a hand-type infrared microphone 32 serving as a transmitter. The receiver 34 is substantially equivalent to the combination of the light receiving sensor and the optical wireless tuner in Non-Patent Document 2. Therefore, the description of the operation of the infrared microphone system 30 is omitted.

  Here, the frequency band of the FM signal used in the infrared microphone system 30 is, for example, an interference or intermodulation product between the frequency band of any one of the uplink channels CH1, CH2, CH3, and CH4 of the infrared conference system 10. It is assumed that the relationship is such that In this case, communication interference occurs between the two, and neither of them can be used at the same time. In view of this, the infrared conference system 10 of the first embodiment, specifically, the center device 12, of the upstream channels CH 1, CH 2, CH 3, and CH 4, is a channel that may cause communication interference with the infrared microphone system 30. By prohibiting the assignment, the channel restriction function that enables simultaneous (parallel) use with the infrared microphone system 30 is provided. Further, as for the uplink channel CH1, CH2, CH3 or CH4 whose allocation is prohibited by this channel restriction function, only the noise is received on the center device 12 side, so that the audio output of the allocation prohibited channel CH1, CH2, CH3 or CH4 is received. The center device 12 is also provided with a voice output prohibiting function for manually prohibiting the voice output. In order to realize this, the center device 12 is configured as follows.

  That is, the infrared conference system 10 includes an input / output terminal 12a to which the coaxial cable 20 is connected as shown in FIG. That is, an upstream FM signal is input from each of the light transmitting / receiving devices 14, 14,... Via the input / output terminal 12a, and a downstream FM signal is transmitted to each of the light transmitting / receiving devices 14, 14,. Each of the light transmitting / receiving devices 14, 14,... Is driven by using DC power supplied from the center device 20 via the coaxial cable 20 as a power source. Therefore, the DC power is applied (superimposed) from the power supply circuit 102 to the input / output terminal 12a via the AC cut low-pass filter (LPF) 100.

  First, the upstream FM signal input to the input / output terminal 12a from each of the light transmitting / receiving devices 14, 14,... Is input to the high pass filter (HPF) 106 and the low pass filter 108 via the DC cut capacitor 104. Here, the cutoff frequency of the high-pass filter 106 is higher than the upper limit frequencies of the downlink channels CH1 and CH2 (a frequency obtained by adding a predetermined bandwidth to 2.25 [MHz]), and the lower limit frequencies of the uplink channels CH1 to CH4. The value is lower than (a frequency obtained by adding a predetermined bandwidth to 7.35 [MHz]), for example, 5.16 [MHz]. On the other hand, the cut-off frequency of the low-pass filter 108 is set to a value lower than the cut-off frequency of the high-pass filter 106 and higher than the lower limit frequencies of the downlink channels CH1 and CH2, for example, 2.70 [MHz]. ing. Accordingly, the upstream FM signal input to the high pass filter 106 via the DC cut capacitor 104 passes through the high pass filter 106 and is input to the distribution circuit 110. The upstream FM signal input to the low pass filter 108 does not pass through the low pass filter 108.

  The uplink FM signal that has passed through the high-pass filter 106 and is input to the distribution circuit 110 is distributed here into four, and four receptions as reception means provided for each of the uplink channels CH1, CH2, CH3, and CH4. Input to the circuits 112, 112,... Each of the receiving circuits 112, 112,... Converts the input upstream FM signal into an intermediate frequency signal having a frequency of 10.7 [MHz], for example, and further performs demodulation processing on the intermediate frequency signal. As a result, the audio signal on which the uplink control data is superimposed is reproduced. The uplink control data and the audio signal are separated from each other. Of these, the uplink control data is input to the control circuit 114, and the audio signal is input to an AF (Audio frequency) amplifier circuit 116. The AF amplifier circuit 116 amplifies the input audio signal, and the amplified audio signal is input to the external speaker via the external output terminal described above. Thereby, the voice of the terminal device 14, 14,..., Which is allowed to speak is output from the external speaker.

  The control circuit 114 has a CPU (Central Processing Unit) (not shown), and analyzes the uplink control data input from the receiving circuits 112, 112,. Then, when the uplink control data represents, for example, a speech request, the control circuit 114 determines whether there is a so-called empty channel that is not currently used (not allocated) among the uplink channels CH1, CH2, CH3, and CH4. Whether there is an empty channel is searched, and downlink control data for permitting a speech is generated using that channel. On the other hand, when there is no empty channel, downlink control data indicating that the speech is not permitted is generated. Whether each of the uplink channels CH1, CH2, CH3, and CH4 is used is determined based on the channel assignment table stored in the memory 118 in the control circuit 114.

  However, four manual channel assignment prohibition switches 120, 120,... Corresponding to the respective uplink channels CH1, CH2, CH3, and CH4 are connected to the control circuit 114, and the control circuit 114 is connected to the channel assignment prohibition switch. The uplink channels CH1, CH2, CH3, or CH4 for which assignment prohibition is set by 120, 120,... Are excluded from assignment targets. For example, when the assignment prohibition is set by the channel assignment prohibition switch 120 corresponding to the uplink channel CH1, an empty channel is searched from the uplink channels CH2, CH3, and CH4 excluding the uplink channel CH1. Accordingly, if the channel allocation prohibition switch 120 sets the allocation prohibition for a channel that may cause communication interference with the infrared microphone system 30 among the upstream channels CH1, CH2, CH3, and CH4, the channel allocation prohibition switch 120 sets the allocation prohibition. It is possible to limit allocation of a channel whose allocation is prohibited. Therefore, it is possible to prevent communication interference with the infrared microphone system 30. That is, a channel restriction function is realized. The channel assignment prohibition switches 120, 120,... Are constituted by, for example, dip switches.

  Further, the uplink control data input to the control circuit 114 from each of the receiving circuits 112, 112,... Has notified the termination of the message from any terminal device 14 that is currently permitted to speak. In some cases, the control circuit 114 cancels the assignment of the uplink channel CH1, CH2, CH3, or CH4 assigned to the terminal device 14. Then, the uplink channel CH1, CH2, CH3, or CH4 whose allocation has been canceled is added to the empty channel. Then, when a request for speech is newly made by any one of the terminal devices 14, any of the free channels is assigned to the terminal device 14 in the manner described above.

  Further, four manual audio output prohibiting switches 122, 122,... Corresponding to the respective upstream channels CH1, CH2, CH3, and CH4 are connected to the control circuit 114. The audio output prohibiting switches 122, 122,... Are for individually invalidating the outputs of the receiving circuits 112, 112,... Of the corresponding channels CH1, CH2, CH3, and CH4. That is, when the audio output prohibition is set by any one of the audio output prohibition switches 122, the control circuit 114 invalidates the reception circuit 112 of the uplink channel CH1, CH2, CH3, or CH4 corresponding to the audio output prohibition switch 122. Specifically, the output of the receiving circuit 112 is cut off. Therefore, for example, when any of the uplink channels CH1, CH2, CH3, and CH4 is set to be prohibited by the channel assignment prohibition switch 120, the reception circuit 112 corresponding to the assignment prohibition channel is connected to the audio output prohibition switch 122. It may be invalidated by operation. By doing so, it is possible to prevent the noise received by the receiving circuit 112 of the allocation prohibited channel from being output. That is, an audio output prohibiting function is realized. The audio output prohibiting switches 122, 122,... Are also constituted by, for example, dip switches.

  The control circuit 114 is connected to a display 124 having a liquid crystal panel configuration, for example. Then, the control circuit 114 displays the status of each channel assignment prohibition switch 120, 120,... And each audio output prohibition switch 122, 122,. Therefore, from the display on the display 124, whether or not the uplink channels CH1, CH2, CH3, and CH4 are prohibited from being assigned, and the respective voice outputs of the uplink channels CH1, CH2, CH3, and CH4 are prohibited. It is possible to grasp whether or not there is.

  The center apparatus 12 includes two transmission circuits 126 and 126 for the respective downlink channels CH1 and CH2. Of these, the audio signal (speech sound) amplified by the AF amplifier circuit 128 is input to the transmission circuit 126 for the downlink channel CH1 as the main audio channel via the AF amplifier circuit 128. Then, the audio signal (simultaneous interpretation sound) is input from the above-described external input terminal to the amplification circuit 126 for the downstream channel CH2 as the sub audio channel via another AF amplification circuit 130. Control data is also input from the control circuit 116 to both the transmission circuits 126 and 126.

  Each of the transmission circuits 126 and 126 performs FSK processing on the input control data, and superimposes the so-called subcarrier signal after the FSK processing on the audio signal input from the amplification circuit 128 or 130. Further, a frequency modulation (FM) process is performed on the audio signal on which the subcarrier signal is superimposed, that is, the mixed signal. As a result, downlink FM signals of the downlink channels CH1 and CH2 are generated, and the generated downlink FM signals are input to the mixed signal 132 and mixed there. Then, the mixed downstream FM signal is sent from the input / output terminal 12a to the light transmitting / receiving devices 14, 14,... Via the low-pass filter 108 and the capacitor 104. The downlink FM signal that has passed through the low-pass filter 108 is also input to the above-described high-pass filter 106. As described above, the cutoff frequency of the high-pass filter 106 is higher than the upper limit frequencies of the downlink channels CH1 and CH2. Value. Therefore, the downstream FM signal input to the high pass filter 106 does not pass through (in other words, reverse flow).

  With reference to FIG. 4, each receiving circuit 112 will be described in a little more detail. As shown in FIG. 4, the reception circuit 112 includes an RF (Radio Frequency) amplifier circuit 200 to which the uplink FM signal distributed by the distribution circuit 110 is input. The uplink FM signal input to the RF amplifier circuit 200 is amplified here and then input to the frequency conversion circuit 202.

  The frequency converter circuit 202 also receives a high-frequency signal having a frequency corresponding to each of the upstream channels CH1, CH2, CH3, and CH4 from the local oscillator circuit 204. Then, the frequency conversion circuit 202 mixes the uplink FM signal input from the RF amplification circuit 200 with the high frequency signal input from the local oscillation circuit 204, and converts it into an intermediate frequency signal having a frequency of 10.7 [MHz]. To do. The converted intermediate frequency signal is amplified by an IF (Intermediate Frequency) amplifier circuit 206 and then input to a demodulation circuit 208.

  The demodulation circuit 208 performs demodulation processing on the input intermediate frequency signal, and generates the above-described mixed signal (upstream audio signal on which the subcarrier signal is superimposed). Then, this mixed signal is input to a separation circuit 210 as separation means, where it is separated into an upstream audio signal and a subcarrier signal. Among these, the upstream audio signal is input to the audio output switch circuit 212. The audio output switch circuit 212 passes (ON) the output of the separation circuit 210 to the above-described AF amplification circuit 116 or shuts off (in accordance with the control of the control circuit 114, in other words, the operation of the corresponding audio output prohibition switch 122. OFF). Therefore, when the audio output switch circuit 212 is ON, the uplink audio signal separated by the separation circuit 210 is input to the AF amplifier circuit 116 via the audio output switch circuit 212 and eventually to the external speaker. Is done. On the other hand, when the audio output switch circuit 212 is OFF, the output of the separation circuit 210 is invalidated, that is, the reception circuit 112 itself is invalidated.

  Also, the subcarrier signal separated by the separation circuit 210 is input to the data demodulation circuit 214, where demodulation processing is performed. As a result, the uplink control data is reproduced, and the reproduced uplink control data is input to the control circuit 114.

  Further, each transmission circuit 126 will be described in detail with reference to FIG. As shown in FIG. 5, the transmission circuit 126 is input to the superimposing circuit 300 serving as mixing means to which the downstream audio signal is input from the AF amplifier circuit 128 or 130. The transmission circuit 126 also includes a data modulation circuit 302 to which downlink control data is input from the control circuit 114. The data modulation circuit 302 also receives a subcarrier signal having a frequency of 24 [kHz] from the sublocal oscillation circuit 304. The data modulation circuit 302 uses this subcarrier signal to perform FSK processing on the downlink control data. Apply. As a result, a subcarrier signal is generated, and the generated subcarrier signal is input to the superposition circuit 300.

  Superimposition circuit 300 superimposes the subcarrier signal input from data modulation circuit 302 on the downstream audio signal input from AF amplification circuit 128 or 130. The downlink audio signal on which the subcarrier signal is superimposed, that is, the above-described mixed signal is further input to the modulation circuit 306. The modulation circuit 306 also receives a carrier signal having a frequency corresponding to each of the downlink channels CH1 and CH2 from the main local oscillation circuit 308. The modulation circuit 306 modulates the frequency of the carrier signal with a mixed signal. As a result, a downlink FM signal is generated, and the generated downlink FM signal is amplified by the RF amplifier circuit 310 and then input to the mixing circuit 132 described above.

  Next, the details of the light transmitting / receiving device 14 will be described with reference to FIG. That is, as shown in FIG. 6, the light transmitting / receiving device 14 includes a terminal 14a to which the coaxial cable 20 is connected, and a downlink FM signal and DC power are input from the center device 12 through the terminal 14a. At the same time, an upstream FM signal is sent out toward the center device 12.

  Among these, the DC power input via the terminal 14 a is input to the power supply circuit 402 via the AC cut low-pass filter 400. The power supply circuit 402 generates a plurality of types (voltage values) of DC power supply voltages Vcc for driving each circuit in the light transmitting / receiving device 14 based on the input DC power.

  The downstream FM signal input via the terminal 14 a is input to the low pass filter 406 and the high pass filter 408 via the DC cut capacitor 404. Here, the cutoff frequency of the low-pass filter 406 is higher than the upper limit frequencies of the downlink channels CH1 and CH2 and lower than the lower limit frequency of the uplink channels CH1 to CH4. For example, 2.70 [MHz] Has been. On the other hand, the cut-off frequency of the high-pass filter 408 is higher than the cut-off frequency of the low-pass filter 406 and lower than the lower limit frequency of the upstream channels CH1 to CH4. For example, 5.16 [MHz] It is said that. Therefore, the downstream FM signal input to the low-pass filter 406 passes through the low-pass filter 406 and is input to the RF amplifier circuit 410. On the other hand, the downlink FM signal input to the high pass filter 408 does not pass through the high pass filter 408.

  The downstream FM signal input to the RF amplifier circuit 410 is amplified here and then input to the light transmission circuit 412. The light transmission circuit 412 includes the above-described infrared light emitting diode, and causes the infrared light emitting diode to emit light according to the downlink FM signal input from the RF amplification circuit 410. That is, luminance modulation is performed. Accordingly, infrared light having a wavelength of 870 [nm] is emitted from the light transmission circuit 412 (infrared light emitting diode).

  The light transmitter / receiver 14 also includes a light receiving circuit 414. The light receiving circuit 414 includes the above-described photodiode, and converts an upstream infrared signal transmitted from each terminal device 18, 18,... Into an electric signal by the photodiode and performs a tuning process on the electric signal. To reproduce the uplink FM signal. The reproduced uplink FM signal is amplified by the RF amplifier circuit 416, then sent to the terminal 14a via the high-pass filter 408 and the capacitor 404, and sent from the terminal 14a to the center device 12.

  The upstream FM signal output from the high pass filter 408 is also input to the low pass filter 406. As described above, the cutoff frequency of the low pass filter 406 is lower than the lower limit frequency of the upstream channels CH1 to CH4. Value. Therefore, the upstream FM signal input to the low-pass filter 406 does not pass through the low-pass filter 406, that is, to the downstream RF amplifier circuit 410. The low-pass filter 406 and the high-pass filter 408 are both high-order (multi-stage) filters. By providing such a high-order filter, the downlink FM signal and the uplink FM signal can be clearly distributed. A high C / N (Carrier / Noise) ratio of [dB] can be obtained.

  Furthermore, with reference to FIG. 7, the detail of each terminal device 18 is demonstrated. As shown in FIG. 7, the terminal device 18 includes a light receiving circuit 500 that receives a downstream infrared signal. The light receiving circuit 500 includes the above-described photodiode for converting the received infrared signal into an electric signal, and further performs a tuning process on the electric signal converted by the photodiode to thereby generate a downlink FM. Reproduce the signal. The reproduced downlink FM signal is amplified by the RF amplification circuit 502 and then input to the frequency conversion circuit 504.

  A high-frequency signal is also input to the frequency conversion circuit 504 from the local oscillation circuit 506. The frequency of the high-frequency signal varies depending on which of the downlink channels CH1 and CH2 is selected by the above-described channel selection switch, and is specifically controlled by a control circuit 508 described later. Then, the frequency conversion circuit 504 mixes the downlink FM signal input from the RF amplification circuit 502 with the high frequency signal input from the local oscillation circuit 506, and converts it to an intermediate frequency signal having a frequency of 10.7 [MHz]. To do. The converted intermediate frequency signal is amplified by IF amplification circuit 510 and then input to demodulation circuit 512.

  The demodulation circuit 512 performs demodulation processing on the input intermediate frequency signal to reproduce the above mixed signal (downstream audio signal on which the subcarrier signal is superimposed). Then, this mixed signal is input to a separation circuit 514 as separation means, where it is separated into a downlink audio signal and a subcarrier signal. Of these, the downstream audio signal is input to the above-described monitor speaker via the AF amplifier circuit 516. As a result, the sound of the channel CH1 or CH2 is output from the monitor speaker. On the other hand, the subcarrier signal is input to a data demodulating circuit 518 where demodulation processing is performed. As a result, the downlink control data is reproduced, and the reproduced downlink control data is input to the control circuit 508.

  The control circuit 508 has a CPU and analyzes the downlink control data input from the data demodulation circuit 518. Here, for example, when the downlink control data is addressed to itself (including its own identification number) and indicates that the speech is permitted, the control circuit 508 enables the output of the microphone 16 to be valid. Turn into. Specifically, the amplifier circuit 520 for amplifying the audio signal output from the microphone 16 is activated. The control data also includes allocation information for the uplink channels CH1 to CH4, and the control circuit 180 controls the local oscillator circuit 522 for uplink according to this allocation information. That is, one of the uplink channels CH1, CH2, CH3, or CH4 is set. As a result, the local oscillation circuit 522 generates a carrier signal having a frequency corresponding to the set up channel CH1, CH2, CH3, or CH4, and the carrier signal is input to the modulation circuit 524.

  The audio signal amplified by the above-described AF amplification circuit 520 is also input to the modulation circuit 524 via a superposition circuit 526 described later. Then, the modulation circuit 524 modulates the frequency of the carrier wave signal input from the local oscillation circuit 522 with the uplink audio signal input from the AF amplification circuit 520 via the superimposing circuit 526. Thus, an uplink FM signal is generated, and the generated uplink FM signal is amplified by the RF amplifier circuit 528 and then input to the light transmission circuit 530. The light transmission circuit 530 includes the above-described infrared light emitting diode as a light emitting unit, and causes the infrared light emitting diode to emit light in accordance with the upstream FM signal input from the RF amplification circuit 528. Thereby, an infrared signal having a wavelength of 870 [nm] is emitted from the infrared light emitting diode.

  Further, the above-described operation panel is connected to the control circuit 508. This operation panel is also provided with a speech end switch (not shown) for notifying the end of speech. When this speech end switch is operated, the control circuit 508 notifies the center device 12 to that effect. Next uplink control data is generated. The uplink control data is input to the data modulation circuit 532, where FSK processing is performed based on the subcarrier signal having a frequency of 24 [kHz] input from the sub local oscillation circuit 534. As a result, a subcarrier signal is generated, and the generated subcarrier signal is input to the superposition circuit 526.

  The superimposing circuit 526 superimposes the subcarrier signal input from the data modulation circuit 532 on the audio signal input from the AF amplifier circuit 520 to generate a mixed signal. Then, this mixed signal is input to the modulation circuit 524 and thereafter processed in the manner described above.

  When the above-described speech request switch provided on the operation panel is operated, the control circuit 508 generates control data indicating that fact. Then, the local oscillation circuit 522 is controlled so that this control data is transmitted on the uplink channel CH1. In this case, a mixed signal including only the subcarrier signal and not including the audio signal is input to the modulation circuit 524, and the subsequent processing is performed as described above.

  By the way, in order to realize the above-described channel limiting function and audio output prohibiting function, the control circuit 114 (CPU) on the center device 12 side performs the channel shown in the flowchart of FIG. 8 according to the control program stored in the memory 118. Execute the assignment control task.

  That is, when a power switch (not shown) of the center device 12 is turned on, the control circuit 114 proceeds to step S1 and confirms the state of each allocation prohibition switch 120, 120,. Then, the process proceeds to step S3, and the above-described channel assignment table is created according to the state of each assignment prohibition switch 120, 120,. That is, which of the uplink channels CH1, CH2, CH3, and CH4 can be allocated and which is prohibited from being allocated is written in the channel allocation table.

  Further, in step S5, the control circuit 114 confirms the state of each audio output prohibition switch 122, 122,. In step S7, the receiving circuits 112, 112,... Are controlled according to the state of the audio output prohibiting switches 122, 122,. To control. In step S9, the control circuit 114 displays the status of each assignment prohibition switch 120, 120,... And each audio output prohibition switch 122, 122,... On the display 124, and then proceeds to step S11.

  In step S11, the control circuit 114 determines whether or not a speech request has been made by any of the terminal devices 18, specifically, whether or not uplink control data representing the speech request has been received. Here, when a speech request is made, the control circuit 114 proceeds to step S13, and searches for an empty channel within an allocatable range among the uplink channels CH1, CH2, CH3, and CH4. In step S15, it is determined whether there is an empty channel.

  Here, when there is an empty channel, the control circuit 114 proceeds to step S17, assigns one of the empty channels to the terminal device 18 that is the requester of speech, and generates downlink control data indicating that the speech is permitted. . In step S19, the contents of the above-described channel assignment table are updated, that is, the fact that a new channel has been assigned to the terminal device 18 that has made the request is written in the channel assignment table. In step S21, the generated downlink control data is transmitted. If there is no empty channel in step S15, the process proceeds to step S23 to generate downlink control data indicating that no speech is permitted to the terminal device 18 that is the request source. And this downlink control data is transmitted by step S21.

  After transmitting the downlink control data in step S21, the control circuit 114 proceeds to step S25, and whether or not a notification to end the speech has been sent from any terminal device 14 that is currently permitted to speak, Specifically, it is determined whether or not uplink control data representing the notice end notification has been received. Here, when the speech end notification is received, the control circuit 114 proceeds to step S27 to update the contents of the channel assignment table, that is, to cancel the channel assignment to the terminal device 18 that is the speech end notification source. Write to the allocation table. In step S29, it is determined whether the power switch is turned off.

  In step S11 described above, if there is no request for speech, the control circuit 114 skips steps S13 to S23 and proceeds directly to step S25. In step S25, if there is no speech end notification, step S27 is skipped and the process proceeds directly to step S29. In step S29, if the power switch is not turned off, the process returns to step S11. If the power switch is turned off, the series of channel assignment control tasks shown in FIG. 8 is terminated. .

  On the other hand, when the above-described speech request switch is operated, the control circuit 508 (CPU) on the terminal device 18 side performs the flowchart of FIG. 9 in accordance with a control program stored in a memory (not shown) built therein. The speech task indicated by is executed.

  That is, when the speech request switch is operated, the control circuit 508 proceeds to step S51, and generates uplink control data indicating that. Then, after setting up the uplink channel CH1 as a specific channel in step S53, uplink control data is transmitted to the center apparatus 12 side using the uplink channel CH1 in step S55.

  Then, the control circuit 508 proceeds to step S57, and determines whether or not a response to the speech request has been made from the center device 12 (control circuit 114) side, that is, whether or not downlink control data including the response has been received. To do. Here, when the response from the center device 12 is confirmed, the control circuit 508 proceeds to step S59 and analyzes the content of the response.

  Then, the control circuit 508 proceeds to step S61, and determines whether or not its own speech is permitted based on the analysis result in step S59 described above. Here, when the speech is permitted, the control circuit 508 proceeds to step S63 and sets the uplink channel CH1, CH2, CH3, or CH4 allocated from the center apparatus 12. In step S65, the microphone 16 is activated. This makes it possible to speak.

  After executing step S65, the control circuit 508 proceeds to step S67, and determines whether or not the above-described speech end switch has been operated. When the speech end switch is operated, that is, when the speech end is instructed, the process proceeds to step S69 and the microphone 16 is invalidated. Further, in step S71, uplink control data for notifying the center device 12 of the end of speech is generated, and in step S73, the uplink control data is transmitted. In step S75, the assigned uplink channel CH1, CH2, CH3, or CH4 is canceled, and the series of speech tasks shown in FIG. 9 ends. Even in the case where the speech is not permitted in step S61 described above, the control circuit 508 ends this series of speech tasks.

  As can be seen from the above description, according to the infrared conference system 10 of the first embodiment, when the infrared microphone system 30 as another system is used at the same time, interference and intermodulation with the infrared microphone system 30 are achieved. When communication interference such as product may occur, such an uplink channel CH1, CH2, CH3, or CH4 may be excluded from allocation targets by manual operation by the channel allocation prohibition switch 120. In this way, the assignment prohibition channel is not used on the infrared conference system 10 side, and the occurrence of the communication interruption can be prevented. That is, both the infrared conference system 10 and the infrared microphone system 30 can be used at the same place at the same time.

  Further, by operating the audio output prohibiting switches 122, 122,..., Unnecessary noise can be prevented from being output. Therefore, comfortable infrared communication without the noise can be realized.

  According to the first embodiment, the infrared microphone 32 of the infrared wireless system 30 which is another system can be actively used as a transmitter for the infrared conference system 10.

  That is, it is assumed that the frequency band of the FM signal used in the infrared microphone 32 (infrared wireless system 30) is the same as the frequency band of any of the upstream channels CH1, CH2, CH3, or CH4 of the infrared conference system 10, for example. . In this case, the uplink channel CH1, CH2, CH3, or CH4 in the frequency band is set as an allocation prohibited channel, and the audio output of the allocation prohibited channel is not prohibited (the audio output prohibition switch 122 is not operated). Then, the FM signal of the infrared microphone 32 is received by the allocation prohibition channel, and the sound thereof is monitored together with the sound of the other upstream channels CH1, CH2, CH3, or CH4. That is, as shown in FIG. 10, the infrared microphone 32 can be incorporated as a transmitter for the infrared conference system 10 at the same level as the terminal devices 18, 18,. This is extremely effective, for example, when a meeting with a presentation is performed.

  However, if the communication interference with other systems is simply avoided, the following configuration may be used, for example. That is, the audio output prohibiting switches 122, 122,... Are omitted from the configuration of FIG. Then, each receiving circuit 112, 112,... Is individually invalidated according to the operation of the channel assignment prohibition switch 120, 120,. That is, the receiving circuit 112 corresponding to the uplink channel CH1, CH2, CH3, or CH4 that is prohibited from being assigned by operating the channel assignment prohibition switch 120 is invalidated. In this way, the trouble of manually operating the audio output prohibiting switches 122, 122,.

  In the first embodiment, the uplink channels CH1, CH2, CH3, and CH4 of the infrared conference system 10 are individually invalidated. However, the present invention is not limited to this. That is, when the frequency band of the infrared microphone system 30 is in a relationship that causes communication interference with either of the downlink channels CH1 and CH2, the downlink channels CH1 and CH2 may be individually invalidated.

  Further, although the center device 12 and the light transmitting / receiving devices 14, 14,... Are configured separately from each other, the present invention is not limited thereto. That is, it is good also as a structure which put these both together in one housing (it united). Further, although the infrared conference system 10 has been described as an example, the present invention is not limited to this. That is, the present invention can be applied to apparatuses other than the infrared conference system 10 as long as the apparatus has a plurality of communication channels.

  The uplink control data is transmitted and received while being superimposed on the uplink audio signal. However, these may be transmitted and received through separate channels. The same applies to the downlink audio signal and downlink control data.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 11, the second embodiment excludes the audio output prohibiting switches 122, 122,... From the configuration of the center device 12 shown in FIG. , 112,... Are excluded. As shown in FIG. 12, a tone detection circuit 216 is provided for each reception circuit 112. Since other than this is the same as that of the first embodiment, the same parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  In other words, in the second embodiment, instead of manual operation by the audio output prohibiting switches 122, 122,..., Each receiving circuit 112, by a so-called tone squelch system that also uses the subcarrier signal included in the upstream FM signal as a tone signal. 112,... Are invalidated individually. For this reason, the tone detection circuit 216 monitors the separation result by the separation circuit 210 and determines whether or not there is a subcarrier signal having a frequency of 24 [kHz]. When the subcarrier signal is detected, it is assumed that the uplink channel CH1, CH2, CH3, or CH4 is assigned, and the audio output switch circuit 212 is turned on. On the other hand, when the subcarrier signal is not detected, it is assumed that the uplink channel CH1, CH2, CH3, or CH4 is not assigned, and the audio output switch circuit 212 is turned off.

  In this way, in the second embodiment, the receiving circuits 112, 112,... Are automatically invalidated by the tone squelch method, so that the trouble of manually operating the audio output prohibiting switches 122, 122,. Further, since the subcarrier signal is also used as a tone signal, it is not necessary to provide a means for generating the tone signal on each terminal device 18 side.

  Note that the uplink channels CH1, CH2, CH3, and CH4 are assigned by inquiring the identification number included in the subcarrier signal (uplink control data), for example, instead of using the subcarrier signal as a simple tone signal. You may make it determine whether it is. In other words, each receiving circuit 112, 112,... May be invalidated by applying a so-called digital code squelch method in which the subcarrier signal is also used as a digital code.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the schematic structure of the whole 1st Embodiment of this invention. FIG. 3 is an illustrative view showing a list of communication channels used in the first embodiment. It is a block diagram which shows schematic structure of the center apparatus in the said 1st Embodiment. It is a block diagram which shows the detail of the receiving circuit in FIG. It is a block diagram which shows the detail of the transmission circuit in FIG. It is a block diagram which shows schematic structure of the light transmission / reception apparatus in the 1st Embodiment. It is a block diagram which shows schematic structure of the terminal device in the said 1st Embodiment. 4 is a flowchart of a channel assignment control task executed by a control circuit on the center device side in the first embodiment. It is a flowchart of the speech task which the control circuit by the side of the terminal device in the 1st embodiment performs. FIG. 3 is an illustrative view showing one application example of the first embodiment. It is a block diagram which shows schematic structure of the center apparatus in 2nd Embodiment of this invention. It is a block diagram which shows the detail of the receiving circuit in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Infrared conference system 12 Center apparatus 14 Transmission / reception apparatus 18 Terminal apparatus 30 Infrared microphone system 114 Control circuit 120 Channel allocation prohibition switch

Claims (3)

A plurality of terminal devices, a light transmitting / receiving device, and a center device are provided,
Any of the terminal devices converts an uplink control data including an identification number representing the terminal device operated by the speech request switch into a first uplink FM signal by operating a speech request switch included in the terminal device. 1 upstream FM signal is converted into a first upstream infrared signal by the first light transmitting means provided in the terminal device, and then emitted,
The light transmitting / receiving device converts a first upstream infrared signal into a first upstream FM signal by a first light receiving means, and transmits the first upstream FM signal to the center device,
The center device demodulates the first uplink FM signal from the light transmitting / receiving device, reproduces the uplink control data, analyzes the uplink control data, makes a request for speech, and the requesting terminal device And when it is possible to speak, it generates downlink control data that includes an identification number representing the requesting terminal device and permits the requesting terminal device to speak, and converts this downlink control data into a first downlink FM signal Transmitted to the light transmitting / receiving device,
The light transmitting / receiving device converts the transmitted first downstream FM signal into a first downstream infrared signal by a second light transmitting means provided in the light transmitting / receiving device, and emits it.
Each terminal device converts the first downstream infrared signal into the first downstream FM signal by the second light receiving means provided therein, reproduces the downstream control data, and sends it to itself from the identification number included therein. Judging what has been done,
The terminal device, to which downlink control data is sent, converts the audio signal into a second uplink FM signal, and the second uplink FM signal is converted into a second infrared uplink signal by the first light transmitting means. Converted to fire,
The light transmitting / receiving device is a first light receiving means that converts a second infrared upstream signal into a second upstream FM signal and transmits it to the center device;
The center device has second uplink FM signal receiving means for converting the second uplink FM signal into a voice signal.
In the infrared communication device,
The center apparatus has a table in which a channel already allocated and a channel whose allocation is prohibited among a plurality of high-frequency channels for the second uplink FM signal are written, and it is recognized that the speech request has been made. When searching for an empty channel among the high-frequency channels based on the table, and there is an empty channel, the downlink control data includes information indicating the empty channel,
The terminal device that is allowed to generate a speech generates a second uplink FM signal of a high frequency channel based on information representing an empty channel included in the downlink control data,
The center device has an allocation prohibition switch for writing a high-frequency channel that causes interference or intermodulation product with the frequency band of the other communication device when used simultaneously with the frequency band of the other communication device as the allocation-prohibited channel in the table. having <br/> infrared communication device. The infrared communication device according to claim 1.
The center device has the same number of second uplink FM signal receiving means as the high-frequency channel,
The audio signal from the second uplink FM signal receiving means is synthesized and converted into a second downlink FM signal of a high-frequency channel different from the high-frequency channels, and the second light-transmitting means of the light transmitting / receiving device. Transmission means for transmitting to
The second light transmitting means of the light transmitting / receiving device converts the second downstream FM signal into a second downstream infrared signal, and emits it to each terminal device,
Each of the terminal devices converts a second downstream infrared signal into a second downstream FM signal by a second light receiving unit, and converts a second downstream FM signal into a voice signal. Have
The center device is an infrared communication device including invalidating means for manually invalidating the receiving means. The infrared communication device according to claim 1.
The center device has the same number of second uplink FM signal receiving means as the high-frequency channel,
The audio signal from the second uplink FM signal receiving means is synthesized and converted into a second downlink FM signal of a high-frequency channel different from the high-frequency channels, and the second light-transmitting means of the light transmitting / receiving device. Transmission means for transmitting to
The second light transmitting means of the light transmitting / receiving device converts the second downstream FM signal into a second downstream infrared signal, and emits it to each terminal device,
Each of the terminal devices converts a second downstream infrared signal into a second downstream FM signal by a second light receiving unit, and converts a second downstream FM signal into a voice signal. Have
The center apparatus determines whether each of the second uplink FM signal receiving means has received a corresponding second uplink FM signal, and determines the second uplink FM signal by the determining means. An infrared communication device comprising: invalidating means for invalidating receiving means determined to be non-received.

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