JPH0391352A - Changeover type interphone set - Google Patents

Abstract

PURPOSE:To improve the reliability of switching operation even when signal leakage exists by providing a call signal relay circuit, a response detection comparator circuit and a reception circuit or the like so as to able to connect a house equipment in first response to a call from a gatedoor unit to the gatedoor unit. CONSTITUTION:When a call signal is sent from a gatedoor unit G1, it is detected by a call signal detection circuit 51, relay contacts RY11, RY12 are changed over. Then a CPU 64 operates a call signal relay circuit 65 to relay a call signal to house units J1, J2 and when a handset 2 is lifted UP by the unit J1, a response signal is returned and received by a reception circuit 61. In this case, even when the response signal is received by a reception circuit 62 due to leakage of the signal, since the reception intensity is low, a response detection comparator circuit 63 decides it that the reception sensitivity of the response signal from the unit J1 is strongest. Thus, the CPU 64 decides the reply from the unit J1 based on the output of the circuit 63, the relay contacts RY11, RY12 are changed over to attain the talking between a unit G1 and the unit J1 and the reliability of the changeover is improved even when the signal leakage exists.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a switching type intercom,
For example, it is suitable for use in a house where two generations live together, where there are two entrances and where there are two families who receive guests.

[Prior Art] Fig. 3 shows a schematic configuration of a conventional intercom with a television. When a visitor operates the call switch 24 provided on the entrance device G, a resistor R3 is connected in parallel to the impedance Z, a calling signal is transmitted to the dwelling unit J, and a ring tone is emitted from the calling speaker 3 of the dwelling unit J. do. When the resident responds to the ring tone by pressing the monitor switch 4, the television camera 2 installed in the entrance device G is connected to the power line L.
1, the video signal is transmitted to the housing unit J via the coaxial cable 1°, and the video is displayed on the monitor TV 1. In addition, the voice signal from the handset 2 of the dwelling device J is transmitted to the entrance device G via the signal line 12 for communication, and the resident's voice is output from the speaker 22 through the two audio transformers of the entrance device G. Ru. On the other hand, the visitor's voice signal inputted by the microphone 23 of the entrance device G passes through an audio amplifier 26, a coupling capacitor 27, a bridge circuit 28, and two audio transformers, and is transmitted via the signal line 12 for communication to the dwelling unit J. The visitor's voice signal is output from the handset 2 of the dwelling unit J. This allows the visitor and the resident to communicate over the phone, and also allows the resident to see the visitor.

Incidentally, an emergency lamp 25 is connected to the entrance device G via a resistor R2, and it is possible to report an abnormality in the house to the entrance side via an emergency report line l.

In this conventional example, in order to connect the housing device J and the entrance device G, a coaxial cable 10 for video signal transmission and a power line 11 are used.
, a signal line 12 for calls and calls, a ground line 13 and an emergency call line 1. A four-core cable is used. For this reason,
The wiring of transmission lines is complicated, and if, for example, only a 2-core or 4-core cable for intercom calls is installed during construction, there is the problem that the wiring will have to be redone when additional TV cameras are installed. Ta.

Figures 4(a) and 4(b) show the schematic structure of another conventional example. This system is constructed by combining a dwelling unit J with a monitor TV 1 installed inside the dwelling unit and an entrance unit G with a TV camera 21 installed at the entrance, both of which are connected using a dedicated cable such as a coaxial cable. transmission line l
connected with. Power is supplied to the entrance unit G side from the housing unit J side, and video, audio, and control signals are multiplexed and transmitted to communicate necessary information.

To explain the more specific configuration, the dwelling unit J is the entrance unit G.
F of the calling signal transmitted in response to the operation of the calling switch 24 of the entrance device G.
A ringing detection circuit 19 that demodulates the M modulated wave, a ringing tone generation circuit 20 that amplifies the demodulated ringing tone and makes the ringing tone sound from the ringing speaker 3, a voice modulation circuit 17 that modulates the voice signal with FM, and an entrance device G. An audio demodulation circuit 13 that demodulates the transmitted FM modulated signal to extract an audio signal, a handset 2 that includes a microphone and a speaker for communications, an audio amplifier 14, 15 that constitutes a communications circuit that includes the handset 2, and a sidetone prevention circuit 16. , a video signal output circuit 11 that extracts the video signal sent out from the entrance device G and outputs it to the monitor television 1, and an FM modulation signal output from the audio modulation circuit 17 through the bandpass filter 18. The FM modulation signal sent out from the door unit G is outputted to the audio demodulation circuit 13 via the bandpass filter 12, the video signal sent out from the entrance unit G is outputted to the video signal output circuit 11 via the video filter 10, Furthermore, the power superimposing circuit 8
A balanced input/output circuit 9 is provided for transmitting the supply voltage to the entrance device G. The audio modulation circuit 17 is configured to perform FM modulation on the transmitted audio signal from the handset 2 and send it out to the transmission line l through the balanced input/output circuit 9. The configuration is such that the FM modulated signal is demodulated and the voice of the entrance device G is output from the handset 2. Further, the video signal transmitted from the entrance device G is outputted to the monitor television 1 after being amplified by the video signal output circuit 11 via the balanced input/output circuit 9 and the video filter 10. A transmission line short-circuit protection circuit 6 and an open detection circuit 7 are added to the power supply superimposition circuit 8.

Further, when the monitor switch 4 is operated, the control circuit 5 is operated, the power supply superimposing circuit 8 is operated, and the power supply device G is supplied with power.

On the other hand, the entrance device G includes an audio demodulation circuit 38 that demodulates the FM modulated signal sent from the housing device J and extracts an audio signal;
Audio modulation circuit 40 that modulates the audio signal from the microphone 23
, a calling signal generating circuit 43 that generates a calling signal in response to the operation of the calling switch 24, an operating state determining circuit 42 that determines the operating state and can generate a calling signal if the call is not in progress, and a voice modulation circuit An FM modulated signal outputted from the circuit 40 via the bandpass filter 41, an FM modulated signal outputted from the calling signal generation circuit 43, and an FM modulated signal outputted from the television camera 21 to the video filter 30 and the video signal output circuit 31.
A balanced input/output circuit 32 inputs a video signal outputted through the transmission line 1 and sends a multiplexed transmission signal to the transmission line 1, and outputs an FM modulated signal to the audio demodulation circuit 38 via a bandpass filter 37; A non-polarizing circuit 33 for non-polarizing the connection with the entrance device G, and a balanced input/output circuit 3 from the modulated signal sent from the housing unit J via the transmission line l.
The power supply separation circuit 34 is provided for separating the power supply of the entrance device G via the power supply terminal 2. The power supply voltage separated by the power supply separation circuit 34 is used as a camera power source and a circuit power source via a power switch circuit 35 and a shunt regulator 36. The audio modulation circuit 40 FM-modulates the audio signal input from the microphone 23 and amplified by the audio amplifier 26 and sends it to the housing unit J via the balanced input/output circuit 32. It is configured to demodulate the FM modulated signal from the circuit 32, amplify it with three audio amplifiers, and output audio from the speaker 22.

In this intercom system, the dwelling device J and the entrance device G are connected by a pair of transmission lines 1 made of coaxial cables, etc., and the video, audio, and video necessary for information communication are transmitted between the two via this transmission line 1. The configuration is such that other control signals are multiplexed and transmitted.

FIG. 5 shows the frequency division state of the signal transmitted via the transmission line 1 in this system.

As shown in the figure, the FM modulated wave of the audio signal sent from the housing device J to the entrance device G is transmitted at the first carrier frequency,
The FM modulated wave of the voice signal sent from the entrance device G to the dwelling unit J is transmitted at the second carrier frequency, and the FM modulated wave of the calling signal is transmitted at the third carrier frequency. The frequency is set to be higher than the video signal frequency band of the television camera that is transmitted over the band.

Note that the power supply voltage is superimposed as a DC component, and these are multiplexed and transmitted via a dedicated transmission line l.

[Problem to be solved by the invention] An intercom system with a TV as shown in Figs. When used in a house where there are two families, two entrance units and two unit units are required. Among these, in order to make a call between one entrance device and one dwelling device, for example, only the entrance device and the dwelling device that are talking can transmit the frequency assigned for transmitting audio signals. A control method can be considered. In this method, all the household appliances and the entrance appliance are always connected, so it is necessary to use a dedicated branch or divider to match the impedance of the transmission line. On the other hand, it is also possible to use a method in which the selected dwelling unit and the entrance unit are switched and connected one-to-one, and the other dwelling unit and entrance unit are disconnected from the transmission line. This method does not require a branch or divider for impedance matching of the transmission line, but it is necessary to select the housing unit and entrance unit to be connected in pairs. First, as for the entrance device, it is sufficient to select the entrance device that generates the calling bow. On the other hand, as for the residential unit, it is preferable to select the residential unit that responded first to the call signal.

By the way, in order to notify the repeater of the response from the residential unit,
As will be described later, it is considered that the high-frequency response signal may be transmitted to the repeater via the transmission line e or another line in the same way as the calling signal. Further, in order to reduce the cost of the dwelling unit and to eliminate the complexity at the time of wiring construction, expansion, or replacement of the dwelling unit, it is preferable that the frequency of the response signal be the same frequency for all the dwelling units. However, if the frequencies of the response signals are the same, the response transmitted from the first unit may be different due to Talostalk on the line, jump in the connection terminal of the repeater or printed wiring board, or signal wraparound. The signal may also leak to the response signal receiving section of the repeater corresponding to the second dwelling unit. If the level of this leakage signal exceeds the detection level of the original response signal, a problem arises in that it becomes the same state as if response signals were transmitted from multiple residential units at the same time, causing malfunction.

The present invention has been made in view of the above points, and its main purpose is to provide a switchable intercom having at least one entrance device and a plurality of dwelling unit devices, in which a call is first received from the entrance device. The purpose is to enable the responding housing unit to be connected to the entrance unit. Another object of the present invention is to realize highly reliable switching operation even in the case of signal leakage in a switching type intercom in which a plurality of residential units use response signals of the same frequency. be.

[Means for Solving the Problems] In order to solve the above problems, in the switchable intercom according to the present invention, as shown in FIG.
,,In an intercom that multiplex transmits at least an audio signal and a video signal between G2 and a residential unit J, J2 using a pair of transmission lines l, at least one entrance unit G, (or G2) and a plurality of residential units Each dwelling unit J, J2 is provided with a means for transmitting a response signal in response to a call from the doorway unit to the repeater K, and the repeater The apparatus is characterized by comprising a receiving means for receiving a response signal from the doorway unit J, J2, and a control means for switching and connecting the dwelling unit from which the response signal to the call from the doorway unit is first received to the doorway unit. It is.

Here, the response signal is a high frequency signal that lasts for a certain period of time,
The frequency is for each housing unit J1. It is preferable to make it common for J2. In this case, if response signals are received from multiple housing units at the same time, the housing unit corresponding to the response signal with the strongest reception strength or the housing unit with a predetermined high priority may be selected.

In the example shown in FIG. 1, there are two entrance devices G.

Although G2 and two housing units J, J2 are used, the number is not limited to the number shown.

[Function] According to the present invention, as described above, the response signal for a call from the entrance device can be transmitted from the dwelling unit to the repeater, so that among the plurality of dwelling units, the response signal is first received by the repeater. By switching and connecting the received dwelling device to the entrance device, it is possible to connect the entrance device for making a call and the dwelling device.

Here, if the response signal from each housing unit is a high-frequency signal with the same frequency, the configuration of each housing unit can be shared, reducing the cost of housing units and making wiring construction, expansion, and replacement easier. . Furthermore, when the repeater is equipped with a response detection means that determines that there is a response when the reception strength of the response signal is above a certain level, this response detection means can be easily shared by each reception means. Become.

On the other hand, if the response signals from each unit are the same frequency,
If there is a signal leakage, the situation will be the same as if there were responses from multiple housing units at the same time, but the reception strength of the response signals is compared and the housing unit corresponding to the response signal with the highest reception strength is selected. There is no risk of malfunction if you do so or select a predetermined device with a high priority.

The more detailed structure and operation of the present invention will become clearer in the following description of the embodiments.

[Embodiment] FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, G,
, G2 is an entrance device, and has the same structure as the entrance device G shown in FIG. 4(b). J, , J2 are housing appliances, and have basically the same configuration as the housing appliance J shown in FIG. 4(,). However, the dwelling units J, , J2 of this embodiment have a function of transmitting a response signal consisting of a high frequency signal lasting a certain period of time to the repeater K multiple times when responding to a call from the entrance unit. The frequency of this high frequency signal is higher than the third carrier frequency shown in FIG. 5, and is set to a common frequency for each of the housing units J, , J2. Note that whether or not the household appliances J, ., J2 have responded to the call from the entrance device is determined by whether or not the handset 2 of the household appliances J, , J2 has been picked up. In other words,
When the hook switch of the handset 2 is set to the hook-up state, the dwelling units J, , J2 transmit a response signal consisting of a high frequency signal that lasts for a certain period of time multiple times. By transmitting the response signal multiple times, the response signal can be reliably detected by the repeater K, thereby increasing reliability.

The repeater is used to switch and connect the transmission line 1 connected to the entrance devices G, .G2 and the transmission line 1 connected to the housing units J, .J2. Reference numerals 51 and 52 are calling signal detection circuits for detecting the calling signals from the entrance devices G, G2.

When the call signal detection circuit 51 detects a call from the entrance device G, the relay contacts Ry, . Line l is connected to relay contact Ry21. Further, when the calling signal detection circuit 52 detects a calling from the entrance device G2, the relay contact Ryl 1 + R'I
+□ is switched in conjunction with the state opposite to the state shown (normally open side), and the transmission line l connected to the entrance device G2 is connected to the relay contact Ry21. In addition, the entrance device G +,
Of the transmission line l connected to G2, relay contact Ry2
．． The transmission line on the side not connected to is connected to a low voltage (for example, DC6V) direct current power source via a resistor, although not particularly shown.

53 is a filter circuit that passes the video signal and audio signal sent from the entrance unit G1 or G2, and 54 is a buffer amplifier that transmits the video signal and audio signal to the housing unit J or J2. Since the response signal is set to a higher frequency than the video signal and audio signal, the filter circuit 5
3, thereby reducing the feedback of the response signal. The output of the buffer amplifier 54 is connected to a relay contact Ry22. Relay contact Ry2.
and Ry22 are linked, and the state shown (normally closed side)
The relay contacts RF3 and Ry4 are controlled individually, and when one housing unit J+ (or J2) is on a call, It operates to disconnect the other housing unit J2 (or J,), and both relay contacts RF 3 and R$' 4 are in the on state during standby when not in use.Relay contacts RV 21 and Ry 22 are in the ON state. The illustrated shape B (
(normally open side), the dwelling unit J1 is directly connected to the entrance unit, the dwelling unit J2 receives the video signal and audio signal from the entrance unit via the buffer amplifier 54, and relay contact Ry 21 , Ry 22 is connected to the state opposite to the state shown in the figure (normally open side), the dwelling unit J2 is directly connected to the entrance unit, and the dwelling unit J is connected to the entrance unit via the buffer amplifier 54. It receives video and audio signals from the device.

61 and 62 are receiving circuits for receiving response signals from the residential units J, ., J2, and are directly connected to the transmission line 1 connected to the residential units J, , J2. The receiving circuits 61 and 62 output a DC voltage at a level corresponding to the reception strength of the received response signal. Reference numeral 63 denotes a response detection comparison circuit, which determines whether the level of the DC voltage output from each receiving circuit 61, 62 exceeds a predetermined value, and if it exceeds a predetermined value, it is determined that there is a response. Furthermore, the level of the DC voltage output from each receiving circuit 61, 62 is compared, and the residential unit J, J2 from which the response signal with the strongest reception strength is received is determined. 64 is a CPU (central processing unit) that controls the overall operation of the repeater. 65 is a calling signal relay circuit;
When the calling signal detection circuit 51 or 52 detects a calling signal from the entrance device G1 or G2, this calling signal is relayed to the dwelling unit devices J1 and J2.

Next, the detailed circuit configuration of the response detection comparison circuit 63 is shown in FIG. 2 and will be described. This circuit consists of operational amplifiers A + , A
The first operational amplifier A is used for detecting the response signal, and the second operational amplifier A2 is used for comparing the response signal.

First, the first operational amplifier A1 is connected to the receiving circuits 61, 62 through an OR circuit consisting of diodes D, D2 and a resistor R1.
connected to the output of

The receiving circuits 61 and 62 receive the response signals S, , S2, respectively, and output DC voltage pulses p, , p2 having a level corresponding to the received strength of the response signals S, , S2. Now, if the level of the DC voltage pulse P1 is higher than the level of the DC voltage pulse P2, the diode D1 is in the conductive state, the diode D2 is in the cutoff state, and the resistor R1 is connected in the order from the DC voltage pulse PI to the diode D1. A voltage with a reduced directional voltage is applied. This voltage is applied to the non-inverting input terminal of operational amplifier A, and compared with the reference voltage Vref applied to the inverting input terminal. If the voltage at the non-inverting input terminal of operational amplifier A1 is greater than or equal to the voltage at the inverting input terminal, the output of operational amplifier A1 will be at a high level; if the voltage at the non-inverting input terminal is less than the voltage at the inverting input terminal, the operational amplifier The output of A1 becomes low level. In other words, if the level of the DC voltage pulse corresponding to the stronger received signal among the response signals S, S2 is greater than or equal to a predetermined value, the output of the operational amplifier A will be at a high level, and if it is less than the predetermined value, the The output of amplifier A1 will be at a low level.

Now, when the output of operational amplifier A1 becomes high level, current flows through resistors R6 and R, and the voltage across resistor R8 rises, so base current flows to transistor Q2, turning on transistor Q2. . This results in resistance R
Collector current flows into transistor Q2 via 7,
The collector potential of transistor Q2 becomes low level. Conversely, when the output of the operational amplifier A becomes low level, the transistor Q2 is turned off, so that the collector potential of the transistor Q2 becomes high level. The collector potential of this transistor Q2 is input to the input port IP2 of the CPU64. On the other hand, the circuit connected to input port IPI operates in the same way by simply replacing resistor R6 with resistors R2 and R3, resistor R8 with resistor R5, resistor R7 with resistor R1, and transistor Q2 with transistor Q1. do. However, the connection point of resistors R2R3 is diode D
3 to the output of the operational amplifier A2, the potential of the input port IPI also changes depending on the output of the operational amplifier A2.

The output of the receiving circuit 62 is connected to the non-inverting input terminal of the operational amplifier A2, and the output of the receiving circuit 62 is connected to the inverting input terminal. Therefore, when the level of the DC voltage pulse P corresponding to the response signal SI is higher than the level of the DC voltage pulse P2 corresponding to the response signal S2, the output of the operational amplifier A2 becomes high level. In addition, the response signal S1
The level of the DC voltage pulse P corresponding to the response signal S2
, the output of operational amplifier A2 is at a low level.

Thereby, the operational amplifier A2 operates as a means for comparing the received strengths of the response signals S, , S2. Second
In the example illustrated in the figure, since the level of the DC voltage pulse P corresponding to the response signal S1 is higher than the level of the DC voltage pulse P2 corresponding to the response signal S2, the operational amplifier A2
output will be at a high level. Therefore, the diode D3 is cut off, and the input ports IPI and IP2 are both at a low level.

On the other hand, when the output of operational amplifier A2 becomes low level, diode D3 becomes conductive and lowers the potential at the connection point of resistors R2 and Rs, so that input port IPI becomes high level and input port IP2 becomes low level.

With the above circuit configuration, response signals can be detected and compared. In the CPU 64, input capo) IPI, IP
2 is detected to determine the presence or absence and magnitude of a response signal. That is, if the input port 1-P2 is at a high level, it is determined that there is no response signal, and if the input port 1-I P2 is at a low level, it is determined that there is a response signal. In the latter case,
Input port ■Detect the state of P1 and input the input port IPI
If the input port IP2 is at a low level, it is determined that the reception strength of the response signal S is strong, and if the input port IP2 is at a high level, the reception strength of the response signal S is determined to be strong.
It is determined that the reception strength of No. 2 is strong.

The operation of this embodiment will be explained below. Now, entrance device G
1, the calling signal is detected by the calling signal detection circuit 51, and the relay contact Ry,
,,Ry,2 are switched to the state shown. C.P.
U64 operates the calling signal relay circuit 65 and relays the calling signal to the dwelling units J, , J2. Thereafter, until the end of the call is detected, the CPU 64 operates the calling signal detection circuit 51.5.
No output from 2 is detected. In the dwelling units J, . . . J2, a calling operation is performed in response to the calling signal sent from the repeater K. At this time, relay contacts R43 and RV4 are both in the on state. In addition, relay contact Ry211 RY 2□
In the illustrated state, the dwelling unit J1 is directly connected to the entrance unit G1. As a result, the entrance device G,
Power is supplied from the housing unit J1. Also, housing equipment J
2 is connected to the entrance device G1 via the buffer amplifier 54, and the video signal and audio signal from the entrance device G can be monitored. Now, when the handset 2 is picked up by the dwelling unit J, a response signal S1 is sent back. This response signal S1 is received by the receiving circuit 61. Further, at this time, the response signal S2 may also be received by the receiving circuit 62 due to signal leakage, but the reception strength thereof is low.

Therefore, the response detection comparison circuit 63 determines that the reception strength of the response signal SI is the strongest. The CPU 64 determines that there is a response from the housing unit J1 based on the output of the response detection comparison circuit 63, and activates the relay contacts Ry2. ．． Switch Ry22 to the illustrated state.

Further, the relay contact R4s remains in the on state, and the relay contact RV< is kept in the off state. For this reason, housing equipment J
2 will no longer be able to talk to the entrance device G1. When the call ends, relay contact Ry3. Ry 4 are both turned on. Moreover, the CPU 64 again detects the call detection circuits 51 and 52.
Return to standby state to detect output.

Next, in addition to the above-described embodiment, when a plurality of household appliances simultaneously respond, the responses may be accepted or accepted according to a predetermined priority order of the household appliances. In this way, there is no need to compare the levels of response signals. For example, as shown in FIG. 1, when there are two residential appliances and there is little line crosstalk and signal leakage occurs only through the buffer amplifier 54, relay contact Ry2. ．． When Ry22 is in the illustrated state, the response signal S from the housing unit J1 may leak to the receiving circuit 62 via the buffer amplifier 54, but the response signal S2 from the housing unit J2 may leak to the receiving circuit 61. There is little possibility. On the contrary, relay contact Ry2. ．． Ry22
When is in a state opposite to the state shown in the figure, even though the response signal S2 from the housing unit J2 may leak to the receiving circuit 61 via the buffer amplifier 54, the response signal S1 from the housing unit J is The possibility of leakage to the receiving circuit 62 is low. In addition, the response signal S is sent simultaneously from two housing units J, J2.
,,S2 is unlikely to occur. Therefore, in such a case, the receiving circuits 61 and 62 simultaneously receive the response signal S.
,, S2 is received, it is determined that there is a response from the dwelling unit directly connected to the entrance unit via the relay contact RV2 or Ry22, and that dwelling unit may be selected as the dwelling unit with a high priority.

Note that in the above example, relay contacts Ry2. ．． The priority order of housing units J, J2 changes depending on the status of Ry22,
The priority order may be fixed in advance.

Also, if the level difference between the response signals is large, the response signal with the highest level is accepted, and only when the level difference between the response signals is small, the response is accepted according to the priority order. A good point is that in the above embodiment, the means (operational amplifier AI) for detecting response signals from multiple dwelling units is shared, but separately from this, the means for detecting response signals from multiple dwelling units is You may also use a method in which each step is performed individually using an independent circuit. In this case, the outputs of multiple response detection circuits are
You will be scanning them one by one using U64. As for the order of the scan, it is preferable to perform response detection for a high priority housing unit before and after response detection for a low priority housing unit. For example, three housing units J1゜J
2 and J3 have the same priority in the same order, Jl, J2. J3. J2. It is preferable to scan the response detection circuit in the order of Jl and repeat this operation at regular intervals. In this way, even if there is a delay in input pulses caused by wiring within the repeater, there is less risk of omission in response detection for residential units with high priority. As a result, if a response signal from a low-priority housing device and a response signal from a high-priority housing device are input at the same time or within a certain period of time, the response signal will be mistakenly assigned to the low-priority housing unit due to failure to detect the response signal. This reduces the possibility that the container will be selected.

[Effects of the Invention] The invention according to claim 1 provides an intercom that multiplex transmits at least an audio signal and a video signal between an entrance device and a dwelling unit using a pair of transmission lines, as described above.
A repeater is provided that switches and connects at least one entrance device and one of the plurality of dwelling unit devices, and the repeater includes means for receiving a response signal to a call from the entrance device, and the response signal is first received. Since the connected dwelling unit is switched and connected to the entrance unit, there is an effect that among the plurality of dwelling unit units, the one that responds first to a call from the entrance unit can be connected to the entrance unit.

In addition, if the response signal from each dwelling unit is made into a high frequency signal that lasts for a certain period of time as in the second aspect of the invention, the response signal can be easily detected by the repeater.

Furthermore, if the response signal detection means is shared as in the third aspect of the invention, the structure of the repeater can be simplified.

Furthermore, if the frequency of the response signal is made the same as in the invention described in claims 4 to 6, the configuration of each housing unit can be made common, so the cost of the housing unit can be reduced, and
Wiring construction, expansion, and replacement are easier. In this case, if there is signal leakage, the situation will be the same as if there were responses from a plurality of household appliances at the same time, but as in the invention described in claim 4, by comparing the received strengths of the response signals, If the housing appliance corresponding to the response signal with the highest reception strength is selected, or if the housing appliance with a predetermined high priority is selected as in the invention described in claim 5 or 6, there is no risk of malfunction. .

Furthermore, as in the invention set forth in claim 7, if the response detection of the dwelling unit with a high priority is performed before and after the response detection of the dwelling unit with a low priority, the response of the dwelling unit with a high priority can be detected. This has the effect that detection can be performed reliably.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a circuit diagram of the same main part as above, Fig. 3 is a schematic configuration diagram of a conventional example, and Fig. 4 (a)
and (b) are block diagrams of a dwelling device and an entrance device in other conventional examples, respectively, and FIG. 5 is an explanatory diagram showing an example of frequency division on a transmission line used in the same. G1. G2 is a doorway device, J2 is a dwelling device, K is a repeater, 61.62 is a receiving circuit, 63 is a response detection comparison circuit, and 64 is a CPU.

Claims (7)

[Claims] (1) In an intercom that multiplex transmits at least an audio signal and a video signal between an entrance device and a dwelling device using a pair of transmission lines, at least one entrance device and one of the plurality of dwelling devices are switched and connected. Each unit is equipped with a means for transmitting a response signal to a call from the entrance unit to the repeater, and the repeater includes a receiving unit for receiving a response signal from each unit, and a means for transmitting a response signal to a call from the entrance unit. 1. A switching type intercom, comprising: control means for switching and connecting a dwelling unit from which a response signal is first received to an entrance unit. (2) The switchable intercom according to claim 1, wherein the response signal is a high frequency signal that lasts for a certain period of time. (3) The repeater further includes a response detection means that determines that there is a response to the call from the entrance device when the reception strength of the response signal is above a certain level, and the response detection means is shared by each reception means. The switchable intercom according to claim 2, characterized in that: (4) The response signals from each dwelling unit are transmitted at the same frequency, the repeater further includes comparison means for comparing the reception strengths of the response signals received from the plurality of dwelling units, and the control means: When response signals from a plurality of dwelling units are received at the same time, the unit switches and connects the dwelling unit from which the response signal determined to have the highest reception strength by the comparison means to the entrance unit. The switching type intercom according to claim 2 or 3. (5) Response signals from each dwelling unit are transmitted at the same frequency, and when response signals from multiple dwelling units are received at the same time, the control means transmits a predetermined high priority dwelling unit to the entrance. 4. The switchable intercom according to claim 2, further comprising means for switching connection to a device. (6) In the case where response signals from a plurality of residential units are received simultaneously, when it is determined that the difference in reception strength of each response signal is within a certain range, the control means is configured to perform a predetermined priority order. 5. The switchable intercom according to claim 4, characterized in that the switchable intercom is used as a means for switchingly connecting a dwelling unit having a high temperature to a doorway unit. (7) The response signals from each dwelling unit are transmitted at the same frequency, and the control means performs the detection operation of the response signal of the dwelling unit with a predetermined high priority to the response signal of the dwelling unit with a low priority. The switching according to claim 2, characterized in that the switching is performed before and after the signal detection operation, and when response signals from a plurality of dwelling units are received, the switching means switches and connects the dwelling unit with a higher priority to the entrance unit. ceremony intercom.