JPH03112257A - Changeover type interphone - Google Patents

Abstract

PURPOSE:To prevent the sneak of a carrier between masters occurring by directly connecting a specific master to a slave, distributing and supplying a signal from the slave to another master and providing an impedance element to attenuate a frequency component in the neighborhood of the carrier. CONSTITUTION:When the master J1 is directly connected to the slave, since the signal from the slave is transmitted to another master J2 via a buffer amplifier 54, and the frequency component for audio signal transmission in the neighborhood of the carrier is attenuated with the impedance element Z1, no sneak of the carrier to the master J1 occurs. Therefore, interference is hard to generate even when the same frequency as that of the carrier from each master is set. Also, by separating the master J2 from the output side of the amplifier 54 when a speech state between the master J1 and the slave is set, and also, short- circuiting a transmission line connected to the master J2 via the impedance element Z2, it is possible to lower the reception level of a high frequency signal from the master J2 at the repeater K compared with a case where the transmission line connected to the master J1 is left being separated, and the inference to the master J1 being set at the speech state with the slave can be eliminated.

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] Figure 2 shows a schematic structure of a conventional intercom with a television. When a visitor operates the call switch 24 provided on the handset G, a resistor R is connected in parallel to the impedance Z, a ringing signal is transmitted to the base unit J, and a ringing tone is emitted from the ringing speaker 3 of the base unit J. sounds. When the resident responds to this ringing tone by pressing the monitor switch 4, power is supplied to the television camera 21 installed in the handset G via the power line p, and the video signal is sent to the coaxial cable! . The video is transmitted to the base unit J via the video monitor J, and the video is displayed on the monitor TV 1. In addition, the audio signal from the handset 2 of the base unit J is transmitted to the slave unit G via the signal line 12 for communication, and the resident's voice is output from the speaker 22 through the audio transformer 29 of the slave unit G. . On the other hand, microphone 23 of handset G
The visitor's audio signal inputted by the audio amplifier 26
The signal is transmitted to the main unit J via the coupling capacitor 27, the bridge circuit 28, and two audio transformers, and the signal line 12 for communication, and the visitor's voice signal is output from the handset 2 of the main unit J. This allows the visitor and the resident to communicate over the phone, and also allows the resident to see the visitor. In addition, an emergency lamp 25 is connected to the handset G via a resistor R2, and an emergency call line! It is possible to report abnormalities in the house to the front door via the .

In this conventional example, in order to connect base unit J and slave unit G,
Coaxial cable for video signal transmission. A four-core cable including a power line 11, a signal line 12 for communication and calling, a ground line 13, and an emergency call line 14 is used.

For this reason, the wiring of transmission lines is complicated, and if, for example, only 2-core or 4-core cables for intercom calls are installed during construction, the wiring must be redone when additional TV cameras are installed. There was a problem.

Figures 3(a) and (1+) show a schematic configuration of another conventional example. This system is configured by combining a base unit J with a monitor TV 1 installed inside the dwelling unit and a slave unit G with a TV camera 21 installed at the front door, both of which are connected to a dedicated cable such as a coaxial cable. transmission line! connected with. Power is supplied to the handset G side from the base phone J side, and video, audio, and control signals are multiplexed and transmitted to communicate necessary information.

To describe a more specific configuration, the base unit J includes a power superimposing circuit 8 for supplying power to the slave unit G, and FM modulation of a calling signal transmitted in response to operation of the call switch 24 of the slave unit G. one ring detection circuit that demodulates the wave, a ring tone generation circuit 20 that amplifies the demodulated ring tone and sounds the ring tone from the ring speaker 3, and a voice modulation circuit 17 that performs FM modulation of the voice signal.
, an audio demodulation circuit 13 that does not demodulate the FM modulated signal sent out from the handset G to extract the audio signal, a handset 2 that includes a microphone and a speaker for phone calls, and an audio amplifier 1415 that constitutes a phone call circuit that includes the handset 2. A sidetone prevention circuit 16 , a video signal output circuit 11 that extracts the video signal sent from the handset G and outputs it to the monitor television 1 , and an FM modulation signal output from the audio modulation circuit 17 through a bandpass filter 18 . While inputting, the child 11jl
The FM modulated signal sent from Q is passed through bandpass filter 1.
2 to the audio demodulation circuit 13, the video signal sent from the handset G to the video signal output circuit 11 through the video filter 10, and the voltage supplied from the power superimposing circuit 8 to the handset G. A balanced input/output circuit 9 for transmission is provided. 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 handset G is output from the handset 2. Further, the video signal transmitted from the handset 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 superimposing circuit 8 is operated, and power is supplied to the handset G.

On the other hand, the handset G includes an audio demodulation circuit 38 that demodulates the FM modulated signal sent from the base unit J to extract an audio signal, and an 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 40. Bandpass filter 41
, the FM modulation signal output from the calling signal generation circuit 43, and the television camera 2.
1 inputs a video signal outputted through a video filter 30 and a video signal output circuit 31 and sends out a multiplexed transmission signal to a transmission line 1, and outputs an FM modulated signal to an audio demodulation circuit 38 via a bandpass filter 37. A balanced input/output circuit 32, a non-polarization circuit 33 for non-polarizing the connection between the transmission line p and the slave unit G, and a
A power source separation circuit 34 is provided for separating the power source of the handset G from the modulated signal sent from the mobile device G via the balanced input/output circuit 32. The power supply voltage separated by the power supply separation circuit 34 is connected to the power switch circuit 35 and the shunt regulator 3.
6 as a camera power source and a circuit power source. In the audio modulation circuit 40, the input from the microphone 23 is sent to the audio amplifier 26.
The amplified audio signal is FM-modulated and sent to the base unit J via the balanced input/output circuit 32, and the audio demodulation circuit 38
It is configured to demodulate the FM modulated signal from the balanced input/output circuit 32, amplify it in the audio amplifier 39, and output audio from the speaker 22.

In this interbon system, a master unit J and a slave unit G are connected by a pair of transmission lines 1 made of coaxial cables, etc., and information and video necessary for communication are transmitted between them via this transmission line 1. , voice, and other control signals are multiplexed and transmitted.

FIG. 4 shows the state of frequency division within 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 base unit J to the slave unit G is transmitted at the first carrier frequency, and the FM modulated wave of the audio signal sent from the slave unit G to the base unit J is transmitted at the first carrier frequency. The FM modulated wave of the calling signal is transmitted at the third carrier frequency.
The signals are transmitted at the A/R rear frequency, and in order to prevent interference, these are set to a higher frequency than the video signal frequency band of the television camera, which is transmitted at the baseband. Note that the power supply voltage is superimposed as a DC component, and these are multiplexed and transmitted via a dedicated transmission line β.

[Problem to be solved by the invention] A television set τ as shown in the double series of Figures 3 (, ) and (b)
When using the 1-ki interpon system in a house where two generations live together, such as a house with two entrances and two families who receive guests, it is necessary to install two slave units and two base units. Is required. Of these, in order to make a call between one handset and one base unit, for example, only the handset and base unit that are talking transmit the frequency assigned for audio signal transmission. A method of controlling this can be considered. In this method, all the master units and slave units 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 base unit and slave unit are switched and connected one-to-one, and the other FF1 units and slave units 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 a parent device and a slave device that are connected one-to-one. As for the handset, it is sufficient to select the handset that generated the calling signal. On the other hand, as for the parent device, it is preferable to select the parent device that first responded to the ejection signal.

By the way, in order to reduce the cost 1- of the base unit and slave units and to eliminate the complexity at the time of expansion or replacement, it is preferable that the carrier waves for transmitting audio signals have the same frequency for all base units. However, if the frequencies of the carrier waves for voice signal transmission are the same, the carrier waves transmitted from one base unit may may leak to other base units. When the level of this leakage signal is high, beats between adjacent frequencies occur due to subtle variations in carrier waves, and unpleasant interference sounds can be heard from the speaker of the slave unit.

In order to prevent such signal leakage, it is desirable to improve the balance of the transmission line, reduce the parallel wiring sections of the transmission line, or increase the distance between the parallel wiring sections, but in actual wiring, , specifications of parallel wiring sections, etc. are often not strictly adhered to. Furthermore, it is difficult to implement a method of forcibly stopping the carrier waves of devices that are not in a talking state due to cost considerations.

The present invention has been made in view of the above points, and its purpose is to enable multiple base units that are switched and connected to at least one slave unit via a repeater to use the same carrier wave for audio transmission. To prevent interference from occurring even when there is carrier wave leakage between base units at a repeater in a frequency switching type intercom.

[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.
, ] 2 and the base unit J, , an intercom that multiplex transmits at least an audio signal and a video signal using a pair of transmission lines between the base unit J, J2, at least one slave unit and a plurality of base units J,
, J2;
Each base unit J, J2 is equipped with a means for bidirectional communication with the slave unit using a carrier wave modulated with an audio signal, and the repeater has a relay contact that directly connects only a specific base unit J (or J2) to the slave unit. R
A switching means such as y2Ry22, a signal distribution means such as a buffer amplifier 54 that distributes the signal from the child unit to another base unit J2 (or Jl) in one direction, and a signal distribution unit connected to the output side of the signal distribution unit. Sound 1 from parent device J2 (or Jl) This device is characterized by comprising an impedance element Z1 that attenuates frequency components near a carrier wave for vehicle signal transmission.

Here, the repeater ■
) from the output side of the signal distribution means, and an impedance element Z2 that short-circuits the transmission line connected to the disconnected base unit J2 (or Jl) at high frequency.

Note that in the example shown in FIG. 1, there are two children II G l ,
G2 and two base units J, , J2 are used, but the number is not limited to the number shown.

[Function] Since the present invention is configured as described above, for example, when the base unit J1 is directly connected to the slave unit, a signal such as the buffer amplifier 54 is sent to the other base unit J2. The signal from the slave unit is transmitted via the distribution means, and the signal is transmitted to the other base unit J2.
Frequency components near the carrier wave for audio signal transmission from the base unit J are attenuated by the impedance element Z1, so that they do not go around to the base unit J, which is not directly connected to the slave unit. Therefore, even if the carrier waves for audio signal transmission from each base unit have the same frequency, interference is unlikely to occur.

Further, when a specific base unit, for example, base unit J, is in a communication state with a slave unit, the other base unit J2 is disconnected from the output side of the signal distribution means, and the transmission line connected to the disconnected base unit J2 is disconnected. If the high frequency is short-circuited via the impedance element Z2, the reception level of the high-frequency signal from the base unit J2 at the repeater I can be lowered compared to the case where the transmission line connected to the base unit J2 is left disconnected. This reduces interference with the base unit J1, which is in communication with the slave unit.

Note that in the above description, J is a specific base unit and J2 is another base unit, but the reverse may be possible.

[Example] FIG. 1 is a diagram of an example of the present invention. In the figure, G
+, G2 is a slave unit, and has the same configuration as slave unit G shown in FIG. 3(b). J + and J 2 are master units, and have basically the same configuration as the master unit J shown in FIG. 3(a). However, the base unit J + of this embodiment,
J2 has a function of transmitting a response signal consisting of a high frequency signal lasting a certain period of time to repeater K multiple times when responding to a call from a slave unit. The frequency of this high-frequency signal is higher than the third carrier frequency shown in FIG. 4, and is set to a common frequency for each base unit J, , J2. Note that whether or not the base unit J,, J2 has responded to the call from the slave unit depends on the base unit J1. It is determined whether the handset 2 of J2 has been picked up. In other words, when the hook switch of the hand cell T-2 enters the hook-up state, the base unit JJ2 transmits 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 (2), increasing reliability.

The transmission line p connected to the repeater I or slave units G, . . . G2 and the transmission line 1 connected to the master unit J, . 51.52 is slave unit G1. This is a calling signal detection circuit for detecting a calling signal from G2. When a call from the call signal detection circuit 51 or the handset G is detected,
Relay contact R3' + +, R)' (2 is switched in conjunction with the illustrated state B (normally closed side), and the transmission line l connected to child unit G1 is connected to relay contact RV2.

Furthermore, when the calling signal detection circuit 52 detects a calling from the handset G2, the relay contacts RV, ..., RV, 2 are turned off in conjunction with the state B (normally open side) opposite to the state shown in the figure. Instead, the transmission line β connected to slave unit G2 is relay contact Ry2.
Connected to +. Note that slave unit G1. 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 slave unit G or G2, and 54 is a buffer amplifier that transmits the video signal and audio signal to parent unit 1tlJ or J2. Since the response signal is set to a higher frequency than the video signal and audio No. 13, it is attenuated by the filter circuit 53, thereby reducing the feedback of the response signal. The output of buffer amplifier 54 is relay contact R3'2
2 and is also grounded via an impedance element 2°. This impedance element Z1 is the carrier wave (fourth
It is designed to have low impedance only for frequencies near the first carrier shown in the figure and high impedance for other frequencies, and is made of, for example, a ceramic trap. Relay contacts Ry21 and R)'22
are interlocked and can be switched between the illustrated state (normally closed side) and the opposite state (normally open side).

Further, relay contacts RVs and RV< are individually controlled, and one parent Ff9. When Jl (or J2) is in a call, it operates to disconnect the other base unit J2 (or Jl), and when it is not in a call and is on standby, both relay contacts RV
3, 'RV<' both switch to the opposite side (normally open side) from the illustrated state. Relay contact Rl'3,
The normally closed contact of RY4 is grounded via impedance element Z2.

This impedance element Z2 is designed to have a low impedance with respect to high frequency signals 6 and is made of, for example, a capacitor. Relay contact RV2. .

When R1+2□ is connected to the state shown (normally closed side), the base unit J is directly connected to the slave unit, and the base unit J2 receives the video signal and audio from the slave unit via the buffer amplifier 54. Upon receiving the signal, relay contact Ry21. When Ry22 is connected to the state opposite to the state shown in the figure (normally open side), the base unit J2 is directly connected to the slave unit, and the base unit J receives power from the slave unit via the buffer amplifier 54. This is a device that receives video and audio signals.

61 and 62 are receiving circuits for receiving response signals from the parent units J, , J, and are directly connected to the transmission line l connected to the parent units 111J, , 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 the predetermined value, it is determined that there is a response.

Furthermore, the levels of the DC voltages output from each receiving circuit 61 and 62 are compared, and the base unit J1. Determine J2. 64 is a CPU (central processing unit), which controls the entire operation of the repeater I. 65 is a calling signal relay circuit, which, when the calling signal detection circuit 51 or 52 detects a calling signal from handset G or G2, relays this calling signal to base devices J and J2.

The operation of this embodiment will be explained below. Now, handset G,
When a ringing signal is sent from the ringing signal detecting circuit 5], the ringing signal is detected by the ringing signal detection circuit 5, and the relay contact Ry +
+, Ry 12 is switched to the state shown. The CPU 64 operates the calling signal relay circuit 65,
The call signal is relayed to base units J, , J2. After that, until the end of the call is detected, the CPU 64 controls the calling signal detection circuit 5.
1.52' output is not detected. The base units JI and J2 perform a calling operation in response to a calling signal sent from the repeater K.

At this time, both relay contacts RV 3 and Rl' + are switched to the normally open side, that is, the state opposite to the state shown in the figure. In addition, relay contact RV21. Assuming that R4'22 is in the illustrated state, the master device J1 is directly connected to the slave device G. As a result, the slave unit G1 has the master unit J.
Power is supplied from 1. Furthermore, the base unit J2 is connected to the slave unit G1 via the buffer amplifier 54, and is in a state where it can monitor the video signal and audio signal from the slave unit G1. However, the output of the buffer amplifier 54 is the impedance element Z.
1, and this impedance element Z
l is the carrier wave (4th
Since it is designed to have low impedance to the frequency and number components near the first carrier in the figure,
The carrier wave of the audio signal sent from the receiver is attenuated. Therefore, the possibility that this carrier wave wraps around to the base unit J1 and causes interference is reduced. Currently, I am using the base unit J1 and the handset 2.
When picked up, a response signal is sent back. This response signal is received by the receiving circuit 61. Further, at this time, a response signal 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 at the receiving circuit 61 is the strongest. CPU64
Now, based on the output of the response detection comparison circuit 63, the main unit J,
It is determined that there is a response from relay contact Ry2. ．． Ry
2 Switch □ to the state shown.

Further, the relay contact R'j3 remains on the normally open side, and the relay contact Ry< is switched to the normally closed side. Therefore, the base unit J2 is no longer supplied with video signals and audio signals from the slave unit G. Furthermore, the transmission line connected to the base unit J2 is short-circuited at high frequency via the impedance element z2. Therefore, the high frequency signals (first carrier, response signal, etc.) sent from the parent device J2 are attenuated. If this impedance element Z2 does not exist, when the base unit J2 is disconnected, the transmission line connected to the base unit J2 will be in a high impedance state, and the high frequency signal on the transmission line will be at a several dB higher level. There is a risk that it may get around to the main unit J.

In this embodiment, by short-circuiting the transmission line connected to the disconnected base unit J2 in terms of high frequency, the level of the high-frequency signal on the transmission line is suppressed to a low level, thereby preventing the signal from going around to the base unit J1 that is in a talking state. There are 0 people. Note that since the impedance element z2 does not short-circuit the transmission line in terms of DC, an excessive DC current does not flow from the base unit J2. When the call ends, relay contact Ry
+ and Ry+ are switched to the illustrated state (normally closed side). Further, the CPU 64 returns to a standby state in which it detects the output of the call detection circuits 51 and 52 again.

[Effects of the Invention] As described above, the present invention provides a switchable intercom equipped with a repeater that switches and connects a plurality of base units to at least one slave unit, in which a specific base unit is directly connected to the slave unit. In addition to distributing and supplying the signal from the slave unit to other base units,
Since an impedance element is provided to attenuate frequency components near the carrier wave for audio signal transmission from the other base unit,
Even if the carrier waves for audio signal transmission of the base units have the same frequency, a simple configuration prevents the carrier waves from wrapping around between the base units.
This has the effect of preventing carrier wave interference.

In addition, when a specific base unit is not in a conversation state with a slave unit,
If you install an impedance element that short-circuits the transmission line connected to the disconnected base unit at high frequency without disconnecting other base units from the slave unit, the transmission line of the disconnected base unit will remain open. Since the level of high-frequency signals on the transmission line of the disconnected base unit is lower than when the base unit is in the state of communication, the effect of reducing the amount of high-frequency signals flowing into the base unit that is in communication with the slave unit is reduced. be.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of a conventional example, and Figs. 3 (a) and (b) are block diagrams of a parent unit and a slave unit in other conventional examples. , FIG. 4 is an explanatory diagram showing an example of frequency division of the transmission line used in the above. Q, , Q2 is a slave unit, Jl, J2 is a master unit, K is a repeater, 2
,．． 22 is an impedance element.

Claims (2)

[Claims] (1) In an intercom that multiplex transmits at least an audio signal and a video signal between a handset and a base unit using a pair of transmission lines, at least one handset and one of the plurality of bases
Each base unit is equipped with a means for bidirectional communication with the slave unit using a carrier wave modulated with an audio signal, and the repeater is a switching means that directly connects only a specific base unit to the slave unit. a signal distribution means for distributing the signal from the slave unit to other base units in one direction; and a signal distribution unit connected to the output side of the signal distribution unit to attenuate frequency components near the carrier wave for audio signal transmission from the base unit. A switchable intercom characterized by comprising an impedance element. (2) The repeater has a means for disconnecting other base units from the output side of the signal distribution means when a specific base unit and slave unit are in a communication state, and a means to connect the transmission line connected to the disconnected base unit with high frequency. 2. The switchable intercom according to claim 1, further comprising an impedance element short-circuited to the impedance element.