JPS5972267A - Communication system of fm carrier type interphone - Google Patents

Abstract

PURPOSE:To secure the privacy telephone function of a two-stage system by transmitting a channel selection signal which consists of pulses whose number corresponds to the number of channels and has the 1st wide-width pulse. CONSTITUTION:A three-stage system consists of master remote systems MR1- MR3 consisting of plural slave equipments R1-R9 and master equipments M1- M3, and a regional master equipment which generalize the master equipments M1-M3; for example, there are eight stations corresponding to No.1-No.8. When the station No.1 calls the station No.8, the channel selection signal which consists of eight pulses with wide pulse width is used for the 1st time and then a communication between the No.1 and No.8 is made by using said channel selection signal. Further, when the station No.8 calls the station No.1, a channel selection signal consisting of one pulse corresponding to the station No.1 is used by the station No.8 to make a communication.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication method, and more particularly to a communication method for an FM carrier intercom that is adapted to the actual situation of society such as the chain of command of a company organization.

In recent years, the spread and development of intercoms has been remarkable, and among them, FM daughter wave transmission type intercoms, which are relatively strong against GfA sounds, have been widely used.

The present inventor has long discovered that the present invention has many features, such as being able to share the carrier frequency for each channel, having a simple circuit configuration, having more channels than conventional intercoms, and being compact and inexpensive. We have researched 10 f communication methods for FM carrier wave intercoms, and as a result of our research, we have found that the master unit usually consists of one base unit (hereinafter referred to as "master") and multiple slave units (hereinafter referred to as one remote). A system that only allows communication between
master/remote system) and multiple systems (7
) A system consisting of all masters with the same level of functionality that allows communication between any all masters (
Patent application No. 131057 (hereinafter referred to as 1 All Master System) (Patent Application No. 131057, No.
No. 135267). Both systems have the following characteristics.

(1) Since a channel select signal is used to switch stations, there is no need for filters or oscillation circuits for carrier frequency switching as in conventional systems, and all It becomes easy to create multiple channels at the same station level, and the interpon manufacturing process can be simplified.

(2) Since the control signal for the low frequency amplification circuit is extracted based on a predetermined signal, there is a very small chance that the low frequency amplification circuit will work due to noise and emit unpleasant sound from the speaker.

(3) In the conventional system, individual fence transmission frequencies were assigned to each station, making it impossible to realize bulk paging; however, in both of the above systems, bulk paging is possible by using a channel select signal common to all stations. This is useful in emergency calls, etc.

(4) In the conventional system, when communication is in progress between specific stations, it is technically difficult to notify the station at the pond that the communication between the specific stations is busy, but in both of the above systems, it is a simple method. This can be achieved through circuit configuration.

(5) When the master and a specific remote are communicating in a master-remote system, or between specific stations in an all-master system, it is possible to prohibit transmission from other remotes and stations with a simple circuit configuration, making it practical. It is convenient.

However, with the master remote system or all master system mentioned above, it is not possible to communicate and communicate in accordance with the actual situation of society in the chain of command of a company organization, and it is difficult to carry out such communication sufficiently. In this case, both of the systems mentioned above must be installed side by side. If this happens, depending on the department, the master and all masters of both systems will be duplicated, which will not only complicate handling but also increase equipment costs.

Therefore, by combining the above two systems, as shown in FIG. ,M2,
Communication method of FM carrier wave intercom (hereinafter referred to as "
The three-tier system is based on the actual situation of society as described above.

The master and all-master of the master-remote system and all-master system are equipped with a select switch that is activated when selecting the remote or other all-master with which you wish to communicate. The select switch (referred to as 1) was a contact type switch.If the conventional master is used as the master M1, M2, and M3 of the three-stage system, a confidential communication function is created between each master M1, M2, and MS. For example, the content of communication between master M1 and remote R1 or between master M1 and all masters M can be heard by masters M2 and M3 of r+b, which is inconvenient in that control of the command chain cannot be maintained. There is.

Therefore, if an attempt is made to maintain a confidential communication function between masters M1, M2, and M3 by improving the conventional master select switch used for masters M, M2, and M3, the structure of the select switch becomes complicated. Moreover, the switch itself becomes large, and as a result, there is a problem that the intercom device becomes large and expensive.

The present invention has been made in view of the above circumstances, and has many of the features shown in (1) to (5) above, as well as considering the actual situation in society regarding the chain of command of a company organization. The purpose of the present invention is to provide a communication method for a three-stage FMi) wave-transmitting intercom that allows contact and communication in accordance with the requirements of the FMI) and maintains a so-called confidential conversation function.

Another object of the present invention is to provide a communication system for an FM carrier intercom that can realize a small and inexpensive intercom by replacing the master select switch with a select circuit composed of electronic switches.

The present invention will be described below with reference to drawings of embodiments.

FIG. 2 shows a channel select signal used in an embodiment of the communication method of the FM carrier type intercom of the three-stage system according to the present invention.

The channel select signal is a signal sent when the transmitting side selects a specific partner station, and the channel select signal is always sent at the beginning of transmission. The channel select signal is composed of a plurality of rectangular pulses, and the number of the pulses cannot be determined depending on the partner station. For example, N
When there are 8 stations corresponding to OI to NO8, N01
When calling the station No. 8 from the station No. 8, a channel select signal consisting of eight pulses is used as shown in Figure 2 (a). From now on, the stations NOI and No. 8 call the channel selection signal consisting of the above eight pulses. Communicate using signals. On the contrary, N
When calling NOI from O8, NO8 calls the NOI by transmitting a channel select signal corresponding to the NOI as shown in FIG.
Communication is performed using a channel select signal consisting of one pulse.

Here, by further specifying that the channel select signal common to all stations (hereinafter referred to as "paging signal") is separate from the channel select signal unique to each station, when a specific station transmits a paging signal, The paging that calls all other stations at once becomes possible.

In this embodiment, the paging signal is composed of nine pulses as shown in r11 in the figure.

FIG. 3 shows a program diagram of an embodiment of a master in a three-stage system FM carrier wave intercom (hereinafter referred to as "device of the present invention") according to the present invention. The intercom according to this embodiment particularly adopts a format in which a carrier wave is transmitted on a power line.

In FIG. 3, TI and T2 are transmitting/receiving terminals connected to the power supply line for transmitting or receiving FM modulated signals, 1 is a bandpass filter, 2A to 2C are low-pass filters,
3A to 3C are voltage limiters, and 3B in particular is a voltage limiter that limits only excessive input and does not limit output signals.
14 is an FM having a received signal input terminal 3, a detected signal output terminal b, a received detection signal output terminal C1 which outputs rLJ when the received signal is input, and "■(" when unmanned), a modulated signal input terminal d, and a carrier wave output terminal e. Detection/modulation circuit, 5 is a low frequency amplification circuit, 6 is a speaker that also serves as a microphone for speaking, Q
1 to Q5 are switching circuits having contacts a, b, c and a control terminal d. In particular, Ql, Q2, Q3 and Q5 are connected between contacts a and b when the control terminal d is "■(", and when rLJ is A switching circuit in which contacts a and c are connected, ■ is connected between contacts λ and 11 (
Switching circuit where contacts λ and C are connected when J, 7
A to 7F are NAND circuits, 8A to 8E are NOR circuits, 9
is the signal rL sent from terminal C of the FM detection/modulation circuit 4.
10 is a burst signal demodulation/mixing circuit which inputs the burst signal outputted from the terminal C of the switching circuit Q4, a demodulation signal output terminal and a specific It has a terminal C that outputs a subcarrier consisting of a frequency, and IIA recovers a burst signal.1) A channel select signal output from the terminal of the hybrid circuit 10 is inputted to input an inhibit signal consisting of a predetermined single pulse. JIB, IIC, and IID are delay circuits that delay the output signal by a predetermined time, and IIE is a channel select signal output from the terminal of the burst signal demodulation/mixing circuit 10 via the NAND circuit 7C. 12 is a waveform shaping circuit which inverts the input signal and shapes the waveform smoothly, and whose output signal rises at the same time as the input signal and whose fall is delayed from the input signal; 12 is the output rHJ of the NOR circuit 8A; The receiver oscillates a pulse having a predetermined pulse width via the delay circuit 11C, inputs the pulse to the terminal of the pulse counting circuit 14 via the NANDM path 7C, and then outputs a signal from the pulse counting circuit 4. is fed back to the control terminal C of 12, thereby stopping its oscillation, and as a result generates the channel select signal shown in FIG. The circuit 14 counts the number of pulses input to the pulse input terminal when the output of the NAND circuit 7B input to the clear terminal & is rLJ, and outputs the output I-.
HJ is sequentially shifted from output terminal C1 to CH9 and output, and as a result, output terminal CHI corresponding to the number of input pulses is output.
~C) Pulse counting circuit that holds one of 19 in rIIJ and clears its output signal when the input of clear terminal 3 is [HJ (Figure 4 shows the operating waveform diagram of pulse counting circuit J4) (A) is the input signal of terminal a, (B) is an example of the channel select signal input to terminal A, e\)
~(g) shows the outputs of the output terminals CHI to CH5 when the pulse shown in (b) is input, and the example shows the output of the output terminals CH6 to CH9 when the pulse shown in (4) is input.
, FF is a flip-flop circuit, 15A is input r I
-I, J, an oscillation circuit that oscillates a pulse of a predetermined frequency; 15B is an oscillation circuit that receives an oscillation output of 15A and outputs an intermittent signal of a predetermined frequency that constitutes a ring tone; L E D I~Ll ;, D9 is a light emitting diode that displays the channel, LEDIO is a light emitting diode that detects the communication status, VR is a variable resistor for preload adjustment, 16A
and 16B are inverters, SWI and SW2 are manual pushbutton return switches for interlocking transmission/reception switching (hereinafter referred to as "IT/L switches") that have three contacts a, b, and c, and SW3 and SW4 are contacts 3, b, and c. This is a manual pushbutton return switch (hereinafter referred to as 1-CALL switch) for generating a ringing tone, which has a structure in which it has a structure that allows it to operate in conjunction with the T/L switch by operating these switches. 17C has a channel select switch corresponding to one channel, and nine input terminals connected to the output terminals CFII to CH9 of the pulse counting circuit 14, and one corresponding to each channel.
9 output terminals connected to the anode of D9 and OR circuit 1
It has an output terminal connected to the input terminal of the 3D and NOR circuit 8E, and further has switches DSI to DS8, which will be described later, corresponding to each channel.
This is a channel select circuit (hereinafter referred to as "rC/S circuit") having a terminal related to connection between each other terminal of S8 and terminal C of T/L switch SWI.

FIG. 5 is a circuit diagram of one embodiment of the C/S circuit 17.

In the figure, C5I, 2.3 and 4 are channel select switches (hereinafter referred to as rC/S switches),
One terminal of the C/S switches C5I to C54 is connected to a resistor 1 (
AND circuits N1-N4 and N5-N8 via 1-R4
It is connected to the other input terminal of the AND circuit Q1 and grounded via resistors R5 to R8, and the other terminal is connected to the output terminal of the AND circuit Q1. One input terminal of the AND circuits N1 to N4 and N5 to N8 are collectively connected to output terminals 3 and b of the reset/select circuit R5. R
S and FS are reset/select times II8 RS reset terminal R and selenium)/Sapling connected to terminal S is an open reset switch and side selection switch, D1 to D
8 is a diode whose anode and cathode are AND
It is connected to the output terminal of the circuits N1 to N8 and the other input terminal.

Therefore, the outputs of AND circuits N1 to N8 are OR circuits 1 to 1.
One input terminal of L8, OR circuits 01 to 08 and AND
Input the other input terminal of 8 to N8KI~, and
It is also input to one input terminal of OR circuit B1.

DSW is switch 1) Sl corresponding to channels 1 to 8.
~DS8, one terminal of the switches DSI~DS8 is connected to the fIIx input terminals of OR circuits 1~L8, respectively, and is grounded via resistors R9~R, ]6. , and the other ends are collectively connected to the terminal C of the T/L switch SWI.

Then, the output of the ORIiI circuit-L8 is input to the other input terminal of the AND circuit M8, and the AND circuit M1 to M
The outputs applied to the output terminals CI-I1 to CH8 of the pulse counting circuit 14 are respectively input to one input terminal of the circuits 8 and 8. In addition, the output that is applied to the output terminal CH9 of the pulse frequency circuit 14 is outputted via the inverter A3.
It is input to one input terminal of the R circuit A1, and is also input to one input terminal of the OR circuit B2 and Pl.

Therefore, the outputs of AND circuits M1 to M8 and 1 to 8 are N.
Input to OR circuit A2 and OR circuit B2, and input to NOR circuit A
2 and I of OR circuit B2]1 power is OR circuit AI and Pl
input to the other and one of the input terminals. The outputs of the OR circuits A1 and Pl are input to the other input terminal of the NOR circuit 8E and one input terminal of the OR circuit 131), respectively.

One input terminal of the OR circuits 01 to 08 is connected to the output terminals Cl-H to CH8 of the pulse counting circuit 14; The input terminals 11 to I8 of the control circuit (hereinafter referred to as 1' LED control circuit) LC are input, and the output of the OR circuit P2 is input to the input terminal I9. r9 has the light emitting diode LED
The anodes of the light emitting diodes LEDI to LEIJ9 are connected together, and the cathodes of the light emitting diodes LEDI to LEIJ9 are collectively connected to the output terminal of the inverter 16B.

Also NORf',! The output of i&3D I is input to one input terminal of the ANI) circuit Q1 and the other input terminal of the OR circuit B2.

Next, the state of the circuit at all times (when not communicating) will be explained.

First, when the reset switch RS is closed, the output terminals 3 and b of the reset/select circuit R5 become r L J
IC NARU (IJ TE AN D times IXN 1~NB (DIJ
It becomes "I power brrr-". Then, OR circuit L]~
The output of L8 and 01 to 08 becomes r L J, and A
N L) The output of 8 is output to circuits M1 to M8 and Kl to [L
'', the outputs of the OR circuits A1 and Pl become ``l'' and rLJ. As a result, the NOR circuit 8E and the OR
The other input and one input of the circuit 13D are "HJ and rLJ
I'll do it.

Also, as the output of N0R1 path B1 becomes "■1", the output of OR circuit B2 becomes rHJ, and therefore the LED
Since the input terminal I9 of the control circuit C becomes [l], the light emitting diode LED9 lights up.

The T/L switches SWI, SW2 and CALL switches SW3, SW4 are connected between contacts a and b, and the switching circuits Ql, Q2, Q3 and Q5 are connected to the control terminal d.
Contacts a and b are connected because HJ is applied, and since Q4 is a control terminal d or rLJ, contacts a and b are connected, and terminal C of FM detection/modulation circuit 4 is not receiving. outputs rHJ and performs burst signal demodulation and
The terminals of the hybrid circuit 10 output rHJ since only the input signal is input to the input terminal a, and the terminal C always outputs the subcarrier (however, one input of the NOR circuit 8B
Since the input terminal λ is 1-L, the channel select signal generating circuit 12 does not oscillate and outputs ☆11. ) Child is “I(”
, and the control terminal C is rHJ, and the oscillation circuit 15
A and 15B are also not oscillating because their inputs are "L".

Next, a case where a specific remote (for example, a remote corresponding to channel 5) is called from the master will be explained.

After the outputs of the AND circuits N1 to N8 are set to rLJ by closing the reset switch R3 as described above, one of the control terminals a and b of the reset select circuit R8 becomes r.
HJ and the other is 1-L. For this reason, C/
When S switch C5I is closed, AND circuit N1 or N5
The output becomes l-HJ, and as described later (LEDI or L
ED5 lights up. Then, the output of the AND circuit N1 is 1
When the output terminals λ and b become 11 and rLJ by closing the selection switch FS, the output of the AND circuit N5 becomes ``■(''. Then, the diode D5 The other input terminal of AND circuit N5 becomes "IFI", and its output is held at rHJ.The 1VL switch SWI is connected between contacts b-7-C, and contact C becomes rLJ. Even if any of the switches DSI to DS8 of dip switch I) SW is closed, the OR circuit]
The other input terminal of L8 becomes rLJ. However, AN
Since the output of the D circuit N5 becomes "I(", the outputs of the OR circuits L5 and 05 become [I(J), so the input terminals of the AND circuit and 5(11 and the input terminal I5 of the LED control circuit circuit) becomes rHJ, and further ANI) circuit K 5
The other input terminal of the NOR circuit B1 becomes 1" HJ, and the output of the NOR circuit B1 becomes rLJ.

Then, input terminal I5 becomes "II]",
The light emitting diode LED5 lights up. In addition, A
N l) After the output of circuit N1 becomes r HJ, C/
Since the fIiL terminal of S switch 1 to C/S switch 4 is set to "L", C/S switch C82 to C3
4 is closed, the outputs of AND circuits N2 to N4 and N6 to N8 remain rLJ.

Then, switch CALI, switches SW'3 and SW4 are turned on. As a result, the 'r/L switches SWI and SW2 are also operated, so that the 7H connection pieces of SWI to SW4 slide to connect the contacts b and c. Therefore, in the 1VL switch SWI, the contact C or rLJ is configured to always indicate 1' HJ, and the output of the NAND circuit 7A, which was always outputting [L], is inverted to "H", and the output of the flip-flop FF is reversed to "H". Set terminal S becomes r HJ 1,
On the other hand, since the reset terminal R is also "I", the output of the output terminal Q of the flip-flop FF is stored in rHJ, and the output of σ is stored in rLJ. In addition, NAND circuit 7A
The output rHJ is inverted by the NAND circuit 7B, and the clear terminal a of the pulse count circuit 14 becomes rLJ. The output of Q is inputted to terminal a of pulse signal generation circuit 12 via NOR circuit 8A and delay circuit 11C, and causes channel select signal generation circuit 12 to oscillate. Here, the delay circuit 11C is a circuit for transmitting the channel select signal later than the carrier wave, as will be described later. At this time, a capacitor connected to a feedback input terminal (not shown) in the channel select signal generation circuit 12 generates a signal.
The voltage is charged to "I(") which is higher than the threshold level before the oscillation starts, and after the output power of the channel select signal generation circuit 12 is reversed to "L", the output terminal starts discharging, and after a predetermined time, the voltage reaches the threshold level.・Since the output reaches the low level and is inverted, after which charging and discharging are repeated between the threshold levels, only the first pulse width of the pulse output from channel select signal generation circuit 2 is wider than the second and subsequent pulses. The width is narrow.The oscillation output of the channel select signal generation circuit 12 is input to the pulse signal input terminal of the pulse counting circuit 14 via the NAND circuit 7C.At this time, the clear terminal 3 of the pulse counting circuit 14 is Since it is rLJ, the pulse counting circuit 14 counts the number of input pulses, and the count output rHJ is sequentially applied to the output terminal.

Then, when the number of input pulses reaches 5, the output terminal C
1F'' is output to H5, and at the same time, this signal is output to the AN
It is input to one input terminal of D circuit M5 and M5. Therefore, the outputs of the AND circuits and 5 become "H", so the outputs of the OR circuits A1 and Pl become rLJ and rHJ. Then, the output of the OR circuit A1 is input to the NORM circuit E, while the output of the OR circuit 1) is input to the control terminal C of the channel select signal generation circuit j2 via the OR circuit 13D and the NAND circuit 7F. As a result, the control terminal C becomes "L" and the channel select signal generating circuit 12 stops oscillating after outputting a predetermined number of pulses. That is, this pulse is the above-mentioned channel select signal. Therefore, by using such a channel select signal, it is possible to easily provide multiple channels without switching the number of 1M peak waves. The channel select signal output from the channel select signal generation circuit 12 is input to the NOR circuit 8B.

In addition, the subcarrier output from terminal C of the burst signal demodulation/mixing circuit 0 is input to one input terminal of the NOR circuit 8B, and based on the above two inputs, the subcarrier is output as a burst signal from the NOR circuit 8B. and its output is OR circuit 1
FM detection/modulation circuit 4 via 3C and low-pass filter 2C
input to the modulation input terminal d. The above burst signal is F
The signal is FM-modulated by the M detection/modulation circuit 4 and output from terminal e with a predetermined time delay behind the carrier wave. On the other hand, the control terminal d of the switching circuit Q3 is the output of the NOR circuit 8A.
)1" is inverted and outputted by the inverter 16A, so it becomes "L", and contacts a and c are connected.

Therefore, the carrier signal output from terminal e of the FM detection/modulation circuit 4 is transmitted through the switching circuit Q3, the voltage limiter 5B (however, in this case, the voltage is not limited as described above), the low-frequency wave transducer 2A, and the band f wave. The signal is output to the power supply line and transmitted via the device I and the transmitting/receiving terminals T1 and T2.

Furthermore, when the CALL switch SW3 is pressed on, the oscillation circuit J5A starts to oscillate, and its output becomes N.
It is input to OR circuits 8c and 8D. However, since one input of the N0R1 path 8D is rHJ, the input of the oscillation circuit 15B is rLJ, so oscillation is stopped, and when the output of the pulse counting circuit 14 becomes rHJ, that is, the channel select After the signal generation circuit 12 stops oscillating, the oscillation circuit 15B starts oscillating. This output signal (hereinafter referred to as the 1st and 11th tone signal) is sent to the OR circuit 13.
After that, it is FM modulated through the same route as the channel select signal, and is transmitted from the transmitting/receiving terminal 1'l and T2 following the channel select signal, and is detected and amplified on the receiving side, and then output from the speaker. Make a ringtone.

The above is an explanation of the operation when calling a specific remote (remote compatible with channel 5) from the master.
Even when the master (11 masters or all masters) is called, a ringing tone signal is transmitted from the same operation.In addition, even in the case of paging, the paging signal and the ringing tone signal are transmitted by the same operation. is sent.

After the remote responds to the call, transmission and reception are performed only by the push returns of the T/L switches SWI and SW2. At this time, at the time of transmission, a channel select signal is always issued first as described above. The audio signal is T
/L switch SW2 is turned on, so S
It is input to the contact C of the switching circuit Q2 via the contact a of W2. At this time, since contacts a and c of Q2 are connected, the audio signal is input to the low frequency amplifier circuit 5 from contact 3 of Q2, and its output is transmitted to the T/L switch SW2, the voltage limiter 3C, and the low frequency offshore wave. The carrier wave output signal is input to the modulation signal input terminal d of the FM detection/modulation circuit 4 through the device 2C, is FM modulated, and the carrier wave output signal is transmitted through the above-mentioned route. However, while the channel select signal is being issued or the ringing tone signal is being issued, the terminals d and rHJ of the switching circuit Q5 are connected, and contacts a and b are connected, or the CALL switch SW4 is connected. As a result of the connection between contacts b and c, the input of the low frequency amplifier circuit 5 is grounded, and therefore, during that period, transmission of audio signals from the master to the remote is prohibited.

Next, a case will be described in which, for example, a remote receives a signal transmitted from the master.

FIG. 6 shows a block diagram of an embodiment of the remote control in the apparatus of the present invention. The configuration is similar to the master shown in FIG. 3, and the same components as the master are designated by the same reference numerals. SW6 is a self-holding multi-pole switch that determines the channel of each remote, and LEDII is a paging display light emitting diode.

7(p) to (e) show operation waveform diagrams of each part of FIG. 6. In this embodiment, the FM carrier signal having the channel select signal first and then the ringing tone signal or audio signal transmitted on the power line is transmitted to the transmitting/receiving terminal 'l'.
I, T2, F
The received signal is input to the received signal input terminal λ of the M detection/modulation circuit 4, and the detected output signal consisting of the burst signal and the ringing tone signal or voice signal is outputted from the terminal. FIG. 7(a) shows the detection output signal of the channel select signal ringing tone signal.

The detection output signal is branched into two directions, one of which is sent to the low-frequency offshore transducer 2B.
, is input to the low frequency amplifier circuit 5 via the volume adjustment VR and the switching circuit Q2, but while the low frequency amplifier circuit 5 is receiving the channel select signal as described later, the input is grounded via the switching circuit Q5. Therefore, the detected output of the channel select signal is not output from the low frequency amplifier circuit 5. Moreover, the other one is input to the contact a of the switching circuit Q4. Here, the terminal C of the FM detection/modulation circuit 4 is connected to r as shown in FIG.
Input LJ to the timer 9 and NAND circuit 7A.

The timer 9 inputs "HJ" to the terminal d of the switching circuit Q4 for a certain period of time ('HJ) as shown in FIG. 7(C) in response to the human input signal 1-L. When the timer output is "H", the channel select signal is
This is the time at which the timer output becomes "L" before inputting to 4. By connecting the contacts a and c of the switching circuit Q4 for a period of time using the output 1'HJ of the timer 9, only the channel select signal among the detection output signals is input to the terminal a of the burst signal demodulation/mixing circuit 10. . At this time, since the channel select signal is transmitted with a certain time delay than the carrier wave as described above, the switching circuit Q5 switches the connection between contacts a and c before the detected output of the channel select signal is input to terminal 3 of Q5. The first part of the channel select signal is never cut. On the other hand, as mentioned above, the FM detection/modulation circuit 4 has a so-called squelch circuit, and even if it receives external noise, if the noise does not have the carrier frequency as its component, the FM detection/modulation circuit 4 Since terminal C of No. 4 does not become rLJ, noise is not input to the burst signal demodulation/mixing circuit 10. Further, the signal rLJ output from the terminal C of the FM detection/modulation circuit 4 is input to the NAND circuit 7A, and the inverted output f''HJ of 7A is input to the set terminal S of the flip-flop FF and also input to the NAND circuit 7B. The inverted output rLJ of 7B is input to the clear terminal 3 of the pulse counting circuit 14, making it possible to count 14. Also, the terminals of the burst signal demodulation/mixing circuit 10 are as shown in FIG. A channel select signal demodulated is output.Due to the circuit configuration of the burst signal demodulation/mixing circuit 10, noise consisting of a frequency other than the subcarrier frequency included in the burst signal is transmitted to the terminal of the burst signal demodulation/mixing circuit 10. 3, no signal is output from the terminal.The demodulated channel select No. 18 is branched into two directions, one is input to the circuit 11A, and this output signal is sent to the reset terminal of the flip-flop FF. Here, the circuit 11A generates a channel select signal (7,) with a width as shown in FIG. This is an inhibit signal generation circuit that generates a narrow single pulse signal (hereinafter referred to as an "inhibit signal") with a predetermined time delay. Therefore, since the inhibit signal generating circuit 11A identifies the width of the input pulse, it does not output the inhibit signal even if a noise pulse having a pulse width shorter than the predetermined time is input, so that the inhibit signal generating circuit 11A does not output the inhibit signal. 5. Prevent malfunctions. The other branch of the demodulated channel select signal is input to the NANDM path 7C, and its inverted output is input to the pulse signal input terminal of the pulse counting circuit 14.

As a result, the pulse counting circuit 14 counts the number of pulses of the pulse signal, and in the description of this embodiment, since a channel select signal having five pulses is transmitted, it outputs r HJ to the output terminal CH5. . At this time,
The multi-pole switch SW6 of each remote (in this embodiment, eight remotes corresponding to channels 1 to 8) is connected to a pulse counting circuit 14 corresponding to the number of channels.
Therefore, only the remote corresponding to channel 5 inputs rHJ outputted to the output terminal CH5 to the OR circuit 13D via the multipolar switch SW6.

Therefore, the count output of the pulse counting circuit 14 is outputted via the multi-pole switch SW6 when the number of pulses corresponding to the number of channels of the pulse counting circuit 14 is input, so that the malfunction of the low frequency amplifier circuit 5 can be prevented as described later. To prevent. The following is the operation of the remote corresponding to channel 5. "I(" outputted to the output terminal CH5 of the pulse counting circuit 4 is inputted to one side of the NAND circuit 7E via the multipolar switch SW6 and the OR circuit 13D.
The output of F is inverted by the rHJ input to the terminal S and the inhibit signal input to the terminal R, and the inverted output 1-BJ of the output terminal Q is output to N via the OR circuit 13A.
Input to AND circuit 7E. The NAND circuit 7E is the same as 2 above.
When the input of Q5 becomes "L" HJ, rLJ is output, and the output signal is inputted to the control terminal d of the switching circuit Q5. Therefore, since the terminal d of Q5 becomes "L", the output signal of Q5 becomes Connect the switch or switching contacts a and c 7. This releases the input grounding of the low frequency amplifier circuit 5, and the detected output signal output from the terminal of the FM detection/modulation circuit 4 after the channel select signal. Since the output signal, that is, the ringing tone signal and the audio signal are amplified by the low frequency amplifier circuit 5 and drive the speaker, the above-mentioned malfunction can be prevented.

In the above, the operation after the channel select signal is input to the pulse counting circuit 14 and "Ill" is output to the output terminal CH5 has been explained only for the IJ mote that has one R and corresponds to channel 5. The operation will be explained. Since the multi-pole switch SW'6 is not connected to the output terminal CH5 of the pulse counting circuit 14 for remotes other than the remote corresponding to channel 5, the rHJ outputted to CH5 as described above is not input to the OR circuit 13 [). . Therefore, rLJ is input to one of the input terminals of the OR circuit 13B, and the oscillation signal output from the oscillation circuit +5A is input to the input terminal of the OR circuit 13B via the NOR circuit 8C. The circuit 13B outputs an oscillation signal, and the light emitting diode LED 10 blinks.In other words, while a specific master and a specific remote are communicating and one of them is transmitting a carrier wave, other masters, remotes, and all Master's light emitting diode L E 1) By blinking, it is possible to indicate to other masters, remotes, and all master operators that a specific master and a specific remote are busy, which is convenient in practice. .

Next, the master sends a paging signal as described above to the IM
The remote reception operation in this case will be explained. The operations from when each remote receives the paging signal to when the signal is input to the pulse counting circuit 14 of each remote are similar to those for the channel select signal described above. However, each remote's pulse counting circuit 1
The output terminal CII 9 of 4 is connected to the input of the OR circuit 13D. Therefore, Figure 2? rHJ, which outputs the 111 output terminal cn9+i by inputting the paging signal consisting of nine pulses to the pulse counting circuit 14 as shown in FIG.
The signal is output via 3D, and the input grounding of the low frequency amplifier circuit 5 is canceled by the above-described operation. Therefore, the ringing signal following the paging signal is transmitted to each remote low frequency amplifier circuit 5.
By amplifying the signal and driving each speaker, it is possible to call all remotes at once.

Next, the case of transmitting from the remote to the master will be explained. The remote transmission operation is basically the same as the master transmission described in T)0. However, since the remote transmits only to the master, there is no manual operation of the C/S switch C5I or the like to generate a specific channel select signal when transmitting from the master. That is, inside each remote device u, there is a sixth
As shown in the figure, the output terminals of the pulse counting circuit 14, the output terminals corresponding to each remote channel, and the OR circuit 1
A multi-pole switch SW6 preset to connect the 3D input terminal is arranged. Therefore, by operating SWI to SW4 of the remote, the electric circuit of the remote operates in the same manner as the master described above, and by connecting the multi-pole switch SW6, the number of channels corresponding to the remote is the same as the number of channels corresponding to the remote. A channel select signal consisting of a pulse is generated and transmitted to the master along with a subsequent ring signal or audio signal.

Next, when transmitting a carrier wave from the master to a specific remote or from the master to another specific master, the remote (specific remote and other remote) or transmission from another master and from the specific remote to the master or other Transmission by an fh station when a carrier wave is being transmitted from a specific master to the master will be explained. In Fig. 6, when the carrier wave is input to the terminal 3 of the FM detection/modulation circuit 4, the output terminal Q of the flip 70-tube FF is rH.
J'12 NOR circuit 8A (1,) manually connected to one side, NOR
As mentioned above, when the output ILJ of the circuit Uδ8A is inverted by the inverter 16A and inputted to the control terminal d of the switching circuit Q3, the contacts a and 0 of Q3 are connected, as shown in FIG. The same applies to the master shown in (the master and the specific master of the song). At this time, even if the T/L switch SWI is pressed, the NAND
Since the output of circuit 7A does not change, it is a flip-flop FF.
The appearance is the previous state. On the other hand, the input of the NOR circuit 8A connected to SWI is rLJ, or the other input is rHJ, so the output of the NOR circuit 8A does not change and r
It's L.J. Therefore, contact 3- of switching circuit Q3
b remains connected, so the FM detection/modulation circuit 4
The transmission wave output from terminal e of is not transmitted. Zunawaji, by prohibiting transmission from other stations when a carrier wave is being transmitted from one of the stations of the master, specified remote, or other specified master, It does not interfere with communication between other specific masters.

FIG. 8 shows a block diagram of an embodiment of the all-master in the apparatus of the present invention. The construction is similar to the master shown in FIG. 3, and the master and circuit components are designated by the same reference numerals. 5W5-1 to 5W5-9 are manual self-holding bush switches each having six contacts a/%-f (corresponding to this), and when the switch is in the off state, contacts a-b and contacts d- e is connected, and in the on state, contacts b and c and contact ef are connected, and contact C of each switch is connected to the anodes of LED1 to LED8.However, the anode of LED9 is connected to the constant voltage line VC.
C), each contact f is connected to the output terminals CII to CH9 of the pulse counting circuit 14, and furthermore, 5W5
Contacts S and E of -1 are connected to contact λ and contact d of next 5W5-2, and contacts S and E of 5W5-2 are connected to contacts a and d of 5W5-3, and thereafter 5W5-9
The contacts 5W5-9 are connected to the constant voltage line CC, the contacts C are connected to the input terminals of the OR circuit 13E, and the contacts C are connected to the input terminals of the OR circuit 13D.

Therefore, the state of the circuit of this all-master at all times (when not communicating), at the time of reception and at the time of transmission is basically the same as that of the master at all-time reception and at the time of transmission, and also The operation of calling a specific master from the master and the paging operation are basically the same as the operation of the master described above.

Next, it will be explained that when any one of a plurality of masters and remote stations is transmitting, transmission from all masters is prohibited.

When a carrier wave is input to the terminal 3 of the FM detection/modulation circuit 4, the output terminal Q of the flip-flop FF inputs "I(" to one of the N0R1 paths 8A, and the output 1-L of the NOR circuit 8A becomes By inverting the inverter 16 and inputting it to the control terminal d of the switching circuit Q3, the contact a of Q3 is
-b is connected as described above. At this time, even if the T/L switch SWI is turned on, the NA
Since the output of the ND circuit 7A does not change, it remains in the state before the output of the flip-flop FF. On the other hand, the input of the NOR circuit 8A connected to SWI becomes "L", but since the other input is r II J, the output of the NOR circuit 8A is changed to rLJ. Therefore, switching circuit Q3
Since contacts a and b remain connected, FM detection and
The carrier wave output from the terminal e of the modulation circuit 4 is not transmitted. In other words, if any one of the multiple master and remote stations is transmitting, transmission from all masters is prohibited, so communication of any of the stations A1 will not be interfered with. .

Next, to explain the reception of the master, in the case of 1, when a predetermined switch among the C/S switches C5J and C54 is closed, the channel select signal corresponding to the master is made ready to be received. The basic operation is the same as in the case of remote reception described above. However, among other masters, remotes, and all masters, the master is the switch DS of the dip switch DSW.
When a channel select signal from a station corresponding to a preselected specific channel is received based on the closing of any switch among WI to DS8, the low frequency amplifier circuit 5 is activated. There is. That is,
One input terminal of the NANDH path 7E is connected to the output terminal of the OR circuit 13A similarly to the remote and all masters, and the other input terminal is connected to the output terminal of the NOR circuit 8E.

Therefore, at the time of reception, the terminal of the T/L switch SWI is set to HJ (as described above), and therefore the other terminals of switches I) Sl to DS9 of the depth switch SW are also set to "1".
]", so for example, when switch DS3 is closed, the output of OR circuit 3 becomes l-HJ.)
Therefore, the other input terminal of the AND circuit is also r.
It's HJ. FIG. 9 is an operational waveform diagram of the master during reception in this state. Here, an arbitrary channel select signal (for example, a channel select signal corresponding to channel 3 as shown in FIG. 9(a)) is N
The process after the output from the AND circuit 7C will be explained. This channel select signal is input to the terminal of the pulse counting circuit 14 and waveform shaping 1! ! l&i) ] IE
Enter 1. 1113 outputs a signal shown in FIG. Then, counting of the number of input pulses is started, and the pulse counting circuit 14 starts counting the number of input pulses.
At the same time, when the output of the output terminal CH3 becomes I HJ, one of the input terminals of the AN■) circuit M3 becomes "H", and its output becomes r 11 J. ), rLJ is output, and this output signal is input to the NOR circuit 8E. Then, the NOR circuit 8E outputs "H,...l" as shown in the same figure).
This output signal is input to the single input terminal of the NAND circuit 7E. At this time, the other input terminal of the NAND circuit 7E is connected to the flip-flop FF as shown in FIG. 01).
Since the signal rHJ output from terminal Q of is input,
The output of the NAND circuit 7E is rH as shown in the same figure.
J to "I," and as a result the switching circuit Q
5 are connected, and the input grounding of the low frequency amplifier circuit 5 is released.

As mentioned above (the output of the NAND circuit 7E is not related to the output of the pulse counting circuit 14, the C/S switch C
Regardless of which switch among SI to C54 is closed, if there is only a call from the remote, for example corresponding to channel 3, the low frequency amplifier circuit 5 will operate and a ring tone will be emitted from the speaker. Therefore, the master operator can respond to this remote II'J output. Furthermore, since the output terminal cx-13 becomes "11", the output of the OR circuit 03 becomes rHJ, and therefore the input terminal I3 of the control circuit LC becomes "11".
'', even if rHJ is not output from the AND circuit N3, the light emitting diode LED3 that displays channel 3 is turned on to notify the master operator that there is a call from the remote of channel 3. Also,
When the C/S switch C53 corresponding to channel 3 is closed and the output of the A N D circuit N3 is rHJ, the output terminal C■■3 of the pulse counting circuit 14 becomes "I" as described above. ”, the output of 3 to the AND circuit will be “
Therefore, the output of OR circuit 1 becomes +'H
Since it becomes J, the output of OR circuit 13D also becomes "l(",
The light emitting diode L E DIO lights up.

Next, reception of the master when the switch DS5 other than the switch DS3 of the depth switch DSW is closed will be explained. In this case, the output of the OR circuit 5 is at "H", and therefore the other input terminal of the AND circuit is at "H". FIG. 10 is an operational waveform diagram during reception by the master in this state. Now, as in the previous case, select any channel select signal (
The following describes what happens after a channel select signal (for example, corresponding to channel 3 similar to the case described above) is output from the NAND circuit 7C.This channel select signal is input to the terminal of the pulse counting circuit 14 and is also input to the waveform shaping circuit 11E. input. From this circuit 11E, the same figure (0
) is output and input to the NOR circuit 8E. Also, counting of the number of input pulses is started, and the circuit 1
At the same time as the output of the output terminal CT13 of No. 4 becomes r 11 J, one input terminal of the AND circuit M3 becomes rHJ.

However, the other input terminal of the AND circuit circuit is rL
J, and the output terminal Ct15 of the circuit 14 is 1-L.
Since 1, one input terminal of the AND circuit is 1-L, and therefore the output of the AND circuit and 3M5 remains 1-L. Therefore, OR [ul circuit
IU) Output signal <I-HJ remains as shown in FIG. 10 pJj, and this output signal is input to the NOR circuit 8E.

Therefore, the output of N0R1 path 8E remains "I," as shown in )) in the same figure, and also NAND II! l#'
47 One input terminal of E is also "LJ. And N
Even if the signal 1-HJ outputted from the terminal Q of the flip-flop FF is input to the other input terminal of the AND circuit 7E as shown in the same figure (e), the output of the NAND circuit 7E will not be as shown in the same figure (e). As a result, the contacts A and B of the switching circuit Q5 remain connected, and the input terminal of the low frequency amplifier circuit 5 remains grounded. Therefore, the low frequency amplifier circuit 5 remains at "H". During operation, no ringing tone is emitted from the speaker.Therefore, the master operator does not respond to this single call.Then, as the output terminal CH3 becomes rHJ, the OR circuit 0
Since the output of 3 becomes r HJ, the light emitting diode LED3 is a point pair, as in the case described in hij.

The station number of Iya's channel is being called from the channel 3 remote, or the channel 3 remote and (
Notify the master operator that the station I'd is communicating with. -L-k, C/corresponding to channel 3
Since the S switch C53 is not closed, as is clear from the above, the output of 3 to the AND circuit is l'L.
Since the output of the OR circuit PI is 1-L, the output of the OR circuit 13D is also ILJ, and therefore the light emitting diode LEDIO blinks.

As explained above, the noteworthy feature of the communication system of the FM carrier type ink-pump according to the present invention is that the number of pulses corresponding to the number of channels is transmitted before the ringing tone signal or voice signal, and Channels are connected by transmitting a channel select signal (>r) with a wide first pulse width, and the receiving side identifies this channel select signal.Furthermore, at the time of reception, in the master and all masters, the carrier wave A control signal is extracted based on identifying the frequency, subcarrier frequency, and first pulse width of the channel select signal to control the low frequency amplification circuit, and in addition to the above, in the case of a remote control, the number of pulses of the channel select signal is extracted. The purpose is to extract the control signal and control the low frequency amplification circuit by identifying the

Furthermore, another notable feature of the communication method of the FM carrier intercom according to the present invention is that the master can communicate with a preselected specific channel by opening or opening a predetermined switch corresponding to each channel. Equipped with a channel select circuit that activates the low frequency amplification circuit when one corresponding channel select word is input, but does not activate the low frequency amplification circuit when a channel select signal other than a specific channel is input. That's what I did.

As described above, this embodiment provides the following effects.

(1) Since a channel select signal is used to switch channels in the master and all masters, there is no need for filters or oscillation circuits for carrier frequency switching as in conventional systems, and the technology can be configured with the same circuit. It is easy to provide multiple channels both physically and economically. Furthermore, since the remote channels are determined only by the multipole switch program, there is no need to have individual filters or oscillation circuits for each, which simplifies the remote manufacturing process.

(2) The control signal of the low frequency amplifier circuit is extracted based on the above three signals in the master, and the above four signals in the remote and all master, so t
11゛The low frequency amplification circuit is activated by the sound, and the chance of emitting unpleasant sound from the speaker is extremely reduced. However, in the device of the present invention, by using a common channel select signal for all remotes, it is possible to make a call all at once, which is useful in emergency calls.

(4) In the conventional system, when specific stations are communicating (E4), it is technically difficult to notify other stations that the specific stations are busy, or This can be realized by constructing a simple circuit 4i1.li.

((5) Furthermore, in the device of the present invention, when communication is in progress between specific stations, it is possible to prohibit transmission from other stations with a simple circuit construction, which is convenient in practice.

(6) Furthermore, in a three-stage system using a conventional master for each master, a secret function can be maintained between each master, so company groups etc. 61! However, since the device of the present invention maintains a secret communication function between each master, it is possible to communicate and communicate in accordance with the actual situation of society, such as the chain of command. A three-stage system is realized.

The intercom according to this embodiment particularly adopts a format in which a carrier wave is transmitted on a power line, but the present invention is not limited to this format. Further, in the above embodiment, an interpon having nine channels was explained, but the communication system according to the present invention increases the number of output terminals of the pulse counting circuit, the number of C/S switches, and the number of poles of a multi-pole switch. It is also possible to add more Nayannels.
It is J-Noh.

In addition, in the first embodiment, the manual self-holding bush switches 5W5-1 to 5W5-9 of the all-master are configured with contact type switches, or the master C/S circuit 17 of this embodiment is not limited to this. A single switch configured in substantially the same manner may also be used.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the concept of a three-stage system, Fig. 2 is a channel selection signal used in an embodiment of the device of the present invention, Fig. 3 is a block diagram of an embodiment of the master in the device of the present invention, and Fig. 4 is an operating waveform diagram of the pulse counting circuit, FIG. 5 is a circuit diagram of an implementation of the master channel selection circuit in the device of the present invention <9η, and FIG. 6 is a block diagram of an embodiment of the remote in the device of the present invention. FIG. 7 is an operational waveform diagram of the pulse counting circuit, FIG. 8 is a block diagram of an embodiment of the all-master in the apparatus of the present invention, and FIGS. 9 and 10 are operational waveform diagrams of the master during reception. Patent applicant Sunny Electronics Co., Ltd. Patent attorney Koji Onishi 386 Figure 9 Figure 10 (c) /-) L, -------------

Claims (10)

[Claims] (1) A system (hereinafter referred to as a "three-tier system") consisting of one master unit, multiple master units that communicate with the master unit, and multiple slave units that communicate with a specific base unit. In the communication system of FM carrier intercom, when a specific base unit calls any one of the general base unit, other base units, and slave units, the base unit is called the general base unit, the 11-port base unit, and so on. A pulse signal consisting of a number of pulses corresponding to the number of channels of any one of the above-mentioned pulses and the number of channels of the slave unit, and the pulse width of the first pulse is wider than the pulse width of the other pulses (hereinafter referred to as "channel select pulse signal"). On the other hand, when any station among the general master unit, other base units, and slave units receives the signal, it identifies the pulse width and number of pulses of the first pulse of the channel select signal. An FM carrier wave type ink-pong communication system characterized in that it is carried out as follows. (2) The transmission of the channel select signal is performed by the first Ti
Continuous pulses output from a channel select signal generation circuit equipped with a Schmitt trigger oscillation circuit that oscillates pulses with a wide pulse width are input to a pulse counting circuit, and the continuous pulses are input to the pulse counting circuit to select among the master unit, other base units, and slave units. The output from the corresponding output terminal is taken out and fed back to the channel select signal generation circuit through the channel select circuit, thereby stopping the oscillation to generate a predetermined channel select signal. A sub-transmission wave of a predetermined frequency outputted from a signal demodulation hybrid circuit is gated with the channel selection signal to form a burst signal, and then modulated by an FM detection/modulation ML''4 circuit. F listed in scope 1
Communication method of M-carrier intercom. (3) Identification of the pulse width of the ]th pulse of the channel select signal received by any one of the above-mentioned master unit, other base units, and slave units is output from the FM detection/modulation circuit. Switching circuit for the U-burst signal of the detection output. 4 to the burst signal demodulation/mixing IiJ path to output channel select No. 45, and if the first pulse width of the channel select signal is longer than a predetermined time, an inhibit signal is generated, and a short 2. A communication system for an FM carrier intercom according to claim 1, characterized in that the communication method is carried out by not causing a problem. (4) The number of pulses of the channel select signal in reception by any one of the Jx recording master unit, other base units, and slave units is determined by the number of pulses Rf Daf18jc
Count the number of pulses of the channel select signal to be input using the pulse counting circuit, and check whether the number of pulses corresponds to the number of channels of any of the stations in the master unit, other base units, and slave units. 1. A communication system for a 1"M9 fluid-feeding interpon according to claim 1, wherein the communication method is performed by determining the following. (5) In the communication method of the FM carrier wave intercom of a three-stage system, when calling all base units and slave units at once from a general base unit, or from a specific base unit to a single master unit, all other base units, and When calling all slave units at once, the signal is common to the general master unit, all base units, and slave units, and is composed of a predetermined number of pulses, and the pulse width of the "th" pulse among the above pulses. It transmits a wide pulse signal (hereinafter referred to as a paging signal), while transmitting a paging signal (hereinafter referred to as a paging signal) to the receiving or controlling master, all other masters, and all children. A communication system for an FM carrier/wave intercom, which is characterized in that reception by a paging signal is performed by identifying the pulse width and number of pulses of the first pulse of a paging signal. (6) In the communication method of the FM carrier wave intercom of the three-stage system, when any station calls the other station, the corresponding stations other than the above will receive the channel select signal from any of the stations mentioned above. A light emitting element blinks based on the pulse counting circuit of the oscillator circuit and the output from the oscillator circuit to indicate that one of the stations is busy, while outputting a carrier wave. A communication system for an FM carrier wave intercom, which is characterized in that it does not cause any interference. (7) In the communication method of the FM carrier wave intercom of the three-stage system, all handsets are connected to each other based on the presence or absence of the carrier frequency, the presence or absence of the subcarrier frequency, and the pulse width of the first pulse of the channel select signal. 1. A communication system for an FM carrier intercom, comprising a low frequency amplification circuit controlled via a switching circuit Q5 by identifying the presence or absence of a signal and the output of a pulse counting circuit. (8) In the communication method of the FM carrier wave intercom of the three-stage system, the master unit outputs the output of the timer circuit operated by the reception detection signal of the FM detection/modulation circuit and the output of the pulse counting circuit which is output via the channel select switch. Pulse counting that outputs based on the communication taking place between the master unit and a specific slave unit by inputting a clear signal based on the output to the clear terminal of the pulse counting circuit. A communication system for an FM carrier wave intercom, characterized in that the output signal of the output terminal of the circuit is cleared, thereby making it impossible to eavesdrop on calls between a base unit and a specific slave unit. (9) In the three-stage system FM $f & wave transmission type ink-pong communication method, the base unit controls the presence or absence of the carrier wave frequency, the presence or absence of the sub-image transmission frequency, and the pulse width of the 1st pulse of the channel select signal. F characterized by comprising a low frequency amplification circuit that is controlled via a switching circuit Q5 by identifying the presence or absence of an inhibit signal generated based on
Communication method of M-carrier intercom. (10) In the communication method of the FM carrier wave intercom of the three-stage system, the base unit sends a channel select signal corresponding to a specific channel selected in advance based on opening or opening of a predetermined switch corresponding to each channel. When a channel select signal other than a specific channel is input, the low frequency amplifier circuit is activated via the switching circuit, while the channel select circuit does not activate the low frequency amplifier circuit via the switching circuit when a channel select signal other than a specific channel is input. An FM carrier intercom communication system characterized by the following features: