JP3440642B2 - TV intercom system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television intercom system, and more specifically, when a door intercom subunit with a camera is monitored from an intercom with a television monitor, a noise sound is not generated from a speaker of the intercom subunit with a camera. TV intercom system.

[0002]

2. Description of the Related Art This type of TV intercom system has a monitor switch, a microphone for talking on the telephone, and an intercom with a TV provided with a speaker, and a call switch, a microphone for talking on the speaker, and a speaker at the entrance. It is configured by installing a door intercom with camera and connecting them with a signal line.

In these intercom systems, when the monitor switch of the intercom with the television is operated, power is supplied from the intercom with the television to the intercom unit with the camera to drive the camera, and at the same time, the amplifier circuits of the microphone and the speaker are turned on. Drive and by this
The video captured by the camera of the intercom with camera is displayed on the monitor TV of the intercom with TV, and the ambient sound collected by the microphone of the intercom with the camera can be heard from the speaker of the intercom with TV. (Video and sound monitor function).

FIG. 9 shows the signal spectrum at the line end in such a TV intercom system. This figure shows an example in which a video signal is a baseband signal and an audio signal is FM-modulated and multiplexed for transmission. The first carrier f1 is modulated by the audio signal from the intercom to the intercom subunit, and the intercom subunit is The second carrier f2 is modulated by the voice signal of the intercom from the device, so-called FM
Different carrier frequencies enable two-way simultaneous communication between the intercom subunit and intercom.

[0005]

However, in the above-mentioned conventional TV intercom system, when the monitor switch is operated from the intercom with TV to monitor the monitor, the microphone on the intercom side is muted, so that the indoor audio Does not leak to the front door, but when power is supplied to the intercom subunit from the intercom side, power is supplied not only to the microphone amplifier circuit but also to the speaker amplifier circuit. At times, there was a problem that pop noise was generated from the speaker of the intercom sub-unit, and it became clear that the camera was monitoring at the entrance.

The present invention has been made in view of the above circumstances, and it is a first object of the present invention to provide a TV intercom system in which hop noise does not occur when a door intercom subunit with a camera is monitored from an intercom with a TV. The purpose of 1. The second object of the present invention is to
It is an object of the present invention to provide a TV intercom system in which a call can be made with high sensitivity at the start of a call or at the time of a call, and a malfunction does not easily occur in the intercom subunit even when receiving noise during standby or monitoring.

[0007]

A television intercom system according to claim 1, which is proposed to achieve the above object, outputs a first carrier to a television intercom during a call, a call, or a standby, and a monitor. An oscillation / modulation circuit that stops the output of the first carrier when the switch is operated is provided, and the carrier level detection that detects the presence or absence of the first carrier sent from the intercom with TV is provided in the intercom subunit with camera. A circuit and a speaker power supply control means for turning off the speaker amplifier when the carrier level detection circuit no longer detects the first carrier.

That is, in this system, the oscillation / modulation circuit provided in the intercom with a television outputs the first carrier at the time of waiting, calling, and talking, and does not output it at the time of monitoring. First
When no carrier is detected, the speaker amplifier is turned off to prevent hop noise from being generated from the speaker of the intercom subunit during monitoring.

The first carrier is used for a call from a TV intercom to a door intercom with camera,
The second carrier carries out a call from the door intercom with camera to the intercom with TV. Also, during standby, the first carrier and the second carrier are generated at the same time, but since the power is not supplied from the intercom with TV, the threshold value of the carrier level detection circuit is not exceeded,
Therefore, the speaker is off.

According to a second aspect of the present invention, the television intercom system outputs the first carrier to the intercom with television at the time of calling, talking or waiting, and when the monitor switch is operated, generates a different third carrier. An oscillating / modulating circuit is provided, and a carrier level detection circuit that detects the presence or absence of a third carrier sent from an intercom with a television is installed in the door intercom with camera, and this carrier level detection circuit detects the third carrier. And a speaker power supply control means for turning off the speaker amplifier.

That is, in this system, the intercom with television outputs the first carrier at the time of calling, talking, and waiting, and at the time of monitoring, outputs the third carrier having a frequency different from those of the first and second carriers. In the intercom subunit with camera, when the third carrier is detected, the speaker amplifier is turned off to prevent pop noise from occurring.

According to the third aspect of the present invention, the television intercom system outputs the first carrier to the intercom with television at the time of calling, talking or waiting, and when the monitor switch is operated, a predetermined frequency from the first carrier is output. The camera-equipped intercom subunit is provided with an automatic frequency adjustment circuit and a comparison circuit in the frequency demodulation circuit.
Since the AFC voltage is output from the automatic frequency adjustment circuit, this voltage is compared and determined by the comparison circuit to determine whether or not the monitor switch has been operated, and when it is determined that the monitor switch has been operated, the speaker power supply control means. Turns off the speaker amplifier, which prevents pop noise. Here, another carrier output from the oscillation frequency shift circuit at the time of monitoring is limited to the range where the adjustment by the automatic frequency adjustment circuit is possible and the change in the output voltage according to the frequency can be determined. It is different from the third carrier proposed in Item 2.

According to a fourth aspect of the present invention, there is provided the television interphone system according to the first aspect, wherein the intercom with television is provided with an output level switching circuit for increasing the output of the oscillation / modulation circuit. , Attendant circuit,
A carrier detection circuit for detecting the first carrier is provided.

That is, in this system, similarly to the system according to claim 1, the intercom with television outputs the first carrier at the time of calling, talking, and waiting, and stops the output of the first carrier at the time of monitoring. However, the output from the output level switching circuit is increased during the period from the start of the call to the end of the call after power is supplied from the intercom with TV after receiving the call from the intercom with camera. In the intercom subunit with camera, when the first carrier exceeding a predetermined threshold value is detected, the attenuation operation by the attenuator circuit is prohibited and the speaker is turned on.

Therefore, after the call from the intercom subunit is answered, the first carrier is superposed on the DC power source supplied from the TV intercom during the period in which a call is made, and the output is further increased by the output level switching circuit. Therefore, the intercom sub-unit can easily detect the start of the call state, and a call with high sensitivity becomes possible. It is desirable that the output adjustment by the output level switching circuit be set to a high level at the beginning of a call in response to a call from the intercom subunit, in order to facilitate detection by the intercom subunit. It is desirable to set a high level within the range that does not adversely affect the.

Further, in this system, during standby, the first carrier level does not exceed the threshold value of the carrier detection circuit because direct current power is not supplied from the intercom with television, and therefore the speaker is caused by the first carrier. It is never turned on. Also, during this standby, the attenuator circuit also performs the attenuation operation, resulting in low sensitivity, and even if noise of a frequency component similar to the first carrier occurs, it is possible to prevent malfunctions and to substantially reduce the system noise margin. Can be increased to

A television intercom system according to a fifth aspect is a further improvement of the television intercom according to the fourth aspect, in which the output level switching circuit makes a call after the call switch of the intercom subunit with camera is operated. The output of the oscillating / modulating circuit is increased only during a predetermined time when is started, and the speaker amplifier is turned on while the carrier level detection circuit detects the first carrier that exceeds the predetermined threshold value. The attenuation operation by the attenuator circuit is prohibited.

That is, in this system, the output level switching circuit provided in the intercom with the television increases the level for a predetermined time in response to the call from the intercom subunit with the camera, and the attenuator circuit of one of the intercom subunit with the camera. Means that the attenuation operation is prohibited when the first carrier exceeds the threshold value of the carrier detection circuit, the speaker is turned on, and the attenuation operation of the attenuator circuit is performed in the standby state. Even if noise having a frequency component close to that of the carrier is generated, it is possible to make the malfunction less likely to occur and substantially increase the noise margin of the system.
Further, in this system, the output level switching circuit increases the signal level for the time until the image is displayed on the monitor TV, so that it is not only easy to detect the start of the call from the intercom subunit, but also , The effect of video beat can be ignored.

A television intercom system according to a sixth aspect is an improvement of the intercom system according to the first aspect, wherein an attenuator circuit is provided on the intercom subunit side.
With a simple structure provided with a carrier level detection circuit for detecting the first carrier, high sensitivity can be maintained during a call and low sensitivity can be maintained during standby. In this system, since the first carrier is not output during monitoring, the carrier level detection circuit does not detect the first carrier even when DC power is supplied from the intercom with a television, so the speaker is off. Then, only the camera and microphone are driven to monitor.

Further, during standby, no DC power is supplied from the intercom with television, so that the first carrier does not exceed the threshold value of the carrier level detection circuit, and the speaker is turned off. Then, at this time, the attenuator circuit performs an attenuation operation, so that even if noise similar to the first carrier comes on the signal line, the attenuator circuit suppresses malfunction and the noise margin increases.

On the other hand, at the beginning of a call and at the time of a call, the first carrier is superposed by the DC power source supplied from the intercom with a television, so that the threshold value of the carrier level detection circuit is exceeded and therefore the speaker is turned on. Becomes Further, at this time, the attenuator circuit also prohibits the attenuation operation, so that the intercom sub-unit can easily detect the start of the call, and the call can be performed at a high level.

According to a seventh aspect of the present invention, there is provided a television intercom system having the features of the first to sixth aspects, wherein the interphone with a television and the intercom subunit with a camera are connected by a two-wire signal line. It has been configured. Such a two-wire intercom system
Used to simplify the wiring structure, carriers (FM modulation) that are modulated with audio signals for two-line signal lines for communication, video signals from cameras, speakers, microphones, and DC power supplies for driving the cameras It is possible to call, make a call while watching a video, and monitor monitoring by transmitting a signal that has been superimposed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of the basic configuration of a television intercom system according to the present invention. As shown in the figure, this TV intercom system includes a TV intercom A installed in a room as a master unit and a door intercom subunit B with a camera installed at the entrance.
And are connected through a two-wire signal line L (L1, L2).

The intercom A with TV has a communication circuit 1
0, a monitor circuit 20, a multiplexing circuit 30 that multiplexes and transmits and receives an audio signal and a video signal, a signal processing unit (CPU) 31 that controls the processing of each unit, and a driving power supply to the intercom subunit B. DC power supply circuit 32 and doorphone subunit B
A chime sound generation circuit 33 and a speaker SP that generate a chime sound when a call from is detected, and a monitor switch SW1 that is operated during monitoring are provided.

The calling circuit 10 includes a microphone M for calling.
I1 and the transmission / modulation circuit 11 for outputting the modulation signal obtained by modulating the first carrier f1 with the voice input by the microphone MI1, and the operation of the transmission / modulation circuit 11 is stopped to make the first carrier f1 Carrier output stopping means 12 for stopping the output of the signal, the mute circuit 13, the speaker SP1 for outputting the sound from the intercom subunit B, and the demodulation circuit 1.
4, a speaker amplifier 15, and a BPF 16 that selects and takes out the second carrier f2 modulated by the sound from the intercom slave B. The monitor circuit 20 includes a television 21 and a display unit drive circuit. 22 and 22. In this embodiment, the output of the first carrier f1 output from the transmission / modulation circuit 11 is stopped by the carrier output stop means 12. However, the transmission / modulation circuit 11 itself receives the first carrier f1. The output may be controlled.

On the other hand, the intercom sub unit B with a camera is provided with a communication circuit 50, a camera circuit 60, a multiplexing circuit 70, and a call switch SW2. In the call circuit 50,
Speaker SP2 that outputs audio from intercom A
A demodulation circuit 51, a carrier level detection circuit 52 for detecting the presence or absence of the first carrier f1 transmitted from the intercom A, a speaker amplifier 53, and a speaker power supply control means 54 for controlling the speaker amplifier 53 to be turned on and off.
And a BPF 55 for selecting and extracting the first carrier modulated by the voice from the intercom A, a microphone MI2 for collecting the sound of the front door during monitoring and inputting the voice of the visitor during a call, and 2 carrier f2 is output,
The second carrier f2 is the sound input from the microphone MI2.
And a transmission / modulation circuit 56 that outputs a modulated signal that is obtained by modulating
And a video signal processing circuit 62.

The basic operation of this two-wire type TV intercom system will be described. During standby, there is no audio signal for a call, so the two-wire signal line L has the first carrier f1 and the second carrier f at the standby voltage level.
2 is superimposed. In this state, when the call switch SW2 of the intercom sub-unit B is operated, the standby voltage level sharply drops. Therefore, the call detection circuit (not shown) of the intercom A detects this state, and the CPU 31 causes the chime. After the sound generation circuit 33 is activated and the chime is sounded, power is supplied from the DC power supply circuit 32 to the two-wire signal line L through the multiplexing circuit 30, and the camera circuit 60 of the intercom sub-unit B is connected. The circuit 50 is driven to display the image captured by the camera 61 on the television 21 of the intercom A, and the speakers SP1 and SP2 and the microphone MI of each other are displayed.
Enables telephone calls using 1, MI2. It is also possible to supply power to the intercom subunit B by operating a call switch (not shown) of the intercom A to start a call.

The voice from the intercom A is the microphone MI.
1, the first carrier f1 is modulated by the oscillation / modulation circuit 11 and output as a modulation signal. In the intercom subunit B that receives this, the demodulation circuit 51 demodulates and outputs a voice signal through the speaker SP2. On the other hand, the sound from the intercom subunit B is input from the microphone MI2,
The oscillation / modulation circuit 56 modulates the second carrier f2 and outputs it as a modulation signal. In the intercom A which received this, it demodulates in the demodulation circuit 14 and outputs a voice signal through the speaker SP1.

Such an intercom system has a video and sound monitor function in addition to the above-mentioned call function, and this function is a feature of the present invention. That is, in the present invention,
When the monitor switch SW1 of the intercom A is operated in the standby state, the CPU 31 controls the carrier output control means 12 so as not to supply power to the transmission / modulation circuit 11, and the first signal from the transmission / modulation circuit 11 is supplied. The output of the carrier f1 of 1 is stopped. Then, the carrier level detection circuit 52 of the intercom subunit B no longer detects the first carrier f1, and therefore the speaker power supply control means 54 turns off the speaker amplifier 53. Next, the intercom A drives the DC power supply circuit 32 to supply power to the two-wire signal line L, so that power is also supplied to the speaker SP2 of the intercom subunit B. At this time, the speaker amplifier 53 Camera 6 does not work because it is off
Only 1 and the microphone MI2 operate. As a result, the image of the surroundings captured by the camera 61 is displayed on the television 21 of the intercom A, and the ambient sound of the intercom subunit B collected is output from the speaker SP1. At this time, since the sound output is controlled on the intercom subunit B side, it is possible to eliminate the mute circuit 13 of the intercom A.

The monitor function is generally a monitor switch S.
Since W1 is operated for a predetermined time (for example, 30 seconds) after being operated, the output of the first carrier f1 by the carrier output control means 12 is also stopped for the predetermined time. Here, although the carrier level detection circuit 52 of the intercom subunit B determines whether or not the first carrier f1 is present, a predetermined threshold value is set and the carrier level is lower than the threshold value. It is also possible to turn off the speaker amplifier 53 by the speaker power supply control means 54 when it becomes low, and turn on the speaker amplifier 53 when the carrier level becomes higher than the threshold value.

2A shows the signal spectrum at the line end at the time of communication and FIG. 2B shows the signal spectrum at the time of monitoring. During a call,
Although the frequency of the first carrier f1 from the intercom A to the intercom slave B and the frequency of the second carrier f2 from the intercom slave B to the intercom A are FM-modulated, the voice can be simultaneously talked. The video signal is a video baseband signal from the intercom subunit B to the intercom A, and is mixed with the audio signal and transmitted.

On the other hand, during monitoring, the output of the first carrier f1 is stopped on the side of the intercom A.
When this is detected on the doorphone subunit B side, the speaker SP2
Since the operation of is stopped and no sound is output, pop noise is not generated. The present invention can also be realized by the following other configurations. Claim 2 proposes this method.
According to this method, when the monitor switch SW1 is operated in the intercom A, the first switch from the oscillation / modulation circuit 11
A third carrier different from the second carrier f1 and the second carrier f1 is generated. Then, the carrier level detection circuit 52 of the intercom subunit B detects the third carrier sent from the intercom, and the speaker power supply control means 54.
Turns off the speaker amplifier 53.

Further, in claim 3, instead of the third carrier, a frequency shifted from the first carrier by a predetermined frequency is used. FIG. 3 is a block diagram showing a system configuration in that case, which is a main part of the intercom subunit B.
1 shows a part of the call circuit 50 of FIG. As shown,
The frequency demodulation circuit 57 of the intercom subunit B includes an automatic frequency adjustment circuit 57a and a comparison circuit 57b.

When the monitor switch SW1 is operated by the intercom A, an oscillation frequency shift circuit included in the oscillation / modulation circuit 11 shifts the first carrier f1 (eg, 65 MHz) by a predetermined amount (6
5 ± Δf MHz) is output. In the intercom sub-unit B that receives this, the automatic frequency adjustment circuit 57a outputs an AFC voltage (automatic frequency adjustment voltage) according to the frequency. Therefore, the comparison circuit 57b uses the AFC voltage to make the first call standby or standby state. The frequency of the carrier f1 or the frequency shifted by the operation of the monitor switch SW1 is determined.
Therefore, the comparison circuit 57b can easily perform the comparison and determination, and when the transition to the monitor mode is determined, the speaker amplifier 53 is turned off.

Next, the intercom system proposed in claims 4 and 5 will be described. This system effectively prevents malfunction due to noise by increasing the sensitivity during a call and decreasing the sensitivity during standby. 4 and 5 are block diagrams showing the main parts of this television intercom system. FIG. 4 shows the configuration of the intercom with a television, and FIG. 5 shows the configuration of the intercom subunit.

The intercom A with television is provided with an output level switching circuit 17 on the output side of the oscillation / modulation circuit 1.
The intercom subunit B has an attenuator circuit 58 provided on the output side of the BPF 55 and a carrier level detection circuit 52 having a predetermined threshold value set on the output side. Here, the output level switching circuit 17 is a CPU
The amplification level is temporarily increased by the command signal from the carrier level detecting circuit 5
In No. 2, when the output from the attenuator circuit 58 exceeds a predetermined threshold value, the speaker power supply control means 54
Is turned on, and when it is lower than the threshold, it is turned off.

In such a system, the intercom subunit B
When the call from is detected, the CPU 31 operates the output level switching circuit 17 to increase the output level. For example, the output level is increased by about 6 to 10 dB. In this way, the first carrier f1 is superposed on the DC power source supplied from the TV intercom A, and the output level is further increased by the output level switching circuit 17, so that the first carrier f1 is used as the intercom. The threshold value of the carrier level detection circuit 52 of the child device B is far exceeded, and the call start state can be easily detected. In addition, the output level is increased by the output level switching circuit 17 even after the call is started in response to the call from the intercom subunit B.
Since 1 is returned to the standby level, that is, the call is continued, the call with high sensitivity is possible.

However, when the call ends and returns to the standby state,
Since the DC power is not supplied from the intercom A with television, the first carrier f1 is detected by the carrier level detection circuit 52.
Of the first carrier f1
Therefore, the speaker SP2 is never turned on. Also, during this standby, the carrier level detection circuit 52 activates the attenuator circuit 58, so that the attenuator circuit 58 performs the attenuation operation, resulting in low sensitivity. Therefore, even if the noise of the frequency component close to the first carrier f1 occurs, the malfunction does not easily occur, and the noise margin of the system can be substantially increased.

In the case of configuring such a system, the output level control of the output level switching circuit 17 is controlled by the intercom A for a predetermined time after the call is started in response to the calling of the intercom subunit B, for example, by a television. It may be limited to the time period until the image appears. FIG. 6 shows a change in voltage level on a signal line in such a system,
(A) shows a monitor, and (b) shows a call. At the time of monitoring, the first carrier f1 is not output, and the DC power supplied from the DC power supply circuit 32 for driving the camera 61 and the microphone MI2 is supplied. The output level of the first carrier f1 superposed on is increased by the output level switching circuit 17 for a predetermined time. For example, if the level is increased by 6 to 10 dB, the level of the first carrier f1 increases for a predetermined time (0.5 to 1 second) immediately after the start of a call until the monitor image is displayed. The effect of the video beat at startup can be ignored.

Further, the attenuator circuit 58 may be made to perform a damping operation at the time of standby and at the start of calling. The operation at this time will be specifically described with reference to FIG. 7 by using numerical values. The normal output level from the oscillation / modulation circuit 11 of the intercom A is 80 dBuV, the output level increased by the output level switching circuit 17 is 10 dB, the loss due to the signal line (2-wire signal line L) is 15 dB, and the attenuation is performed by the attenuator circuit 58. The output level to be turned on is 10 dB, and the threshold for turning on the speaker amplifier 53 of the carrier level detection circuit 52 is 65 dBuV.

In such a system, the intercom subunit B
When the intercom A responds to the call by supplying the DC power, the first carrier f1 superimposed on the DC power is 80 dB, and the first carrier f1 is set to 1 by the output level switching circuit 17.
Since it increases by 0 dB, a predetermined time (0.
During 5 to 1 second), 90 dB is output to the signal line, and therefore the first carrier f1 output from the signal line is 75 dBuV. At this time, the attenuator circuit 58 is used.
Performs an attenuation operation, the first carrier f1 detected by the carrier level detection circuit 52 becomes 65 dBuV, and the speaker amplifier 53 is turned on.

During a call, the output level switching circuit 17
Is deactivated, but the attenuation operation of the attenuator circuit 58 is also prohibited, so that the first carrier f1 detected by the carrier level detection circuit 52 becomes 65dBuV,
The speaker amplifier 53 is turned on, and a call is made with the same sensitivity as when the call was started. On the other hand, during standby, the output level switching circuit 17 is inactive, and the attenuator circuit 58
Performs the attenuation operation, the carrier level detection circuit 52 does not operate even if noise similar to that of the first carrier f1 occurs or 80 dB noise occurs at the input end of the signal line.
The level detected by is 65 dB, which is 8
For noise of a level lower than 0 dB, malfunction is prevented, and as a result, a system with a large noise margin is realized.

In the above intercom system, the configuration in which the output level switching circuit 17 is provided on the side of the intercom A with television has been described, but it is possible to provide the carrier level detection circuit and the attenuator circuit on the side of the intercom subunit B with camera. It can be configured to switch to high sensitivity when calling or talking and low sensitivity when waiting. FIG. 8 shows the configuration of the intercom subunit B, which is the main part of this system.

The attenuator circuit 5 is connected to the signal line (2-wire type signal line L) connecting the intercom A and the intercom subunit B.
9 is provided, and this output is input to the carrier level detection circuit 52. This attenuator circuit 59 is an intercom subunit B.
When the call switch SW2 is operated, or when the carrier level detection circuit 52 detects the first carrier f1 exceeding the threshold value, the damping operation is prohibited.

During standby, the carrier level detection circuit 52
Since the first carrier f1 detected by does not exceed the threshold value, the transistor TR1 is turned on, so that the attenuator circuit 59 is attenuated by the voltage dividing circuit of the resistors R1 and R2 (low sensitivity). The speaker power control means 54 turns off the speaker amplifier 53. However, if the call switch SW2 is operated in this state,
Since the transistor TR1 is turned off, the attenuation operation by the attenuator circuit 59 is prohibited. After that, power is supplied from the intercom A side responding to the call, and when the carrier level detection circuit 52 of the intercom subunit B detects the first carrier f1 that exceeds the threshold value, the speaker power control means 54 controls the speaker amplifier 53. Since the transistor TR1 is turned off while being turned on, the damping operation is continuously prohibited. As a result, a call will be started with high sensitivity and a call will also be made, but the call will end,
When the power supply from the intercom A is stopped, the first carrier f1 becomes lower than the threshold value of the carrier level detection circuit 52, the transistor TR1 is turned on again, and the attenuator circuit 59 starts the attenuation operation again, The speaker SP2 is turned off. Therefore, since the sensitivity is low, it is possible to provide a system in which even if noise having a frequency close to that of the first carrier f1 is generated, the noise is suppressed, and a malfunction does not easily occur due to the noise.

[0046]

As can be understood from the above description, according to the television intercom system of claims 1 to 3 of the present invention, when the monitor switch of the intercom with television is operated, the intercom subunit with camera is operated. Since the power is supplied after the speaker is turned off, pop noise does not occur from the speaker of the intercom subunit, and there is no case where the person at the front door knows that the camera is monitoring.

Further, since the speaker is kept in the off state during monitoring, a mute circuit for muting the microphone of the intercom with a television is not required and the structure can be simplified. According to the television intercom system according to any one of claims 4 to 6, in the intercom system according to claim 1 in which the first carrier is not output only during monitoring, generation of pop noise from the intercom subunit can be prevented during monitoring. In addition, since the sensitivity can be high at the start of a call and during a call and low at the time of standby, the system margin against noise can be improved without malfunction even when receiving strong external noise.

In particular, according to claim 5, since the output level is increased only for the predetermined time immediately after the start of the call, it becomes easier to detect the start of the call by the intercom subunit, and the first carrier is also displayed on the television. Since the level becomes high when the power is turned on until the image is displayed, the influence of the image beat can be ignored and the monitor image is not disturbed. Also,
According to claim 6, a simple structure in which the carrier level detection circuit and the attenuator circuit are provided on the slave unit without providing a special output level switching circuit on the intercom side,
By setting high sensitivity during calls and low sensitivity during standby, it is possible to realize an intercom system that is less likely to malfunction due to noise.

A television intercom system according to claim 7 is the one in which the method according to any one of claims 1 to 6 is applied to a two-wire type TV intercom system, and an advantage as a two-line type TV intercom system is further added. ,
It has high commercial value.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a television intercom system according to the present invention.

2 (a) and 2 (b) are diagrams showing a frequency spectrum at a line end of the television intercom system according to the present invention.

FIG. 3 is a block diagram showing a main part of an intercom subunit with a camera in another television intercom system according to the present invention.

FIG. 4 is a block diagram showing a main part of an intercom with a television in another television intercom system according to the present invention.

FIG. 5 is a block diagram showing a main part of an intercom subunit with a camera in another television intercom system according to the present invention.

FIG. 6 is a time chart showing changes in the voltage level of a signal line in another television intercom system according to the present invention, in which (a) shows monitor monitoring and (b) shows call.

FIG. 7 is a diagram showing a level change of a first carrier in another television intercom system according to the present invention.

FIG. 8 is a block diagram showing a main part of an intercom subunit with a camera in another TV intercom system according to the present invention.

FIG. 9 is a diagram showing a frequency spectrum at a line end of a conventional TV intercom system.

[Explanation of symbols]

A: Intercom with TV 10 ... Calling circuit 11 ... Oscillation / modulation circuit 12: Carrier output control means 17 ... Output level switching circuit 20 ... Monitor circuit 21 ... TV 30 ... Multiplexing circuit 31 ... Signal processing unit (CPU) 32 ... DC power supply circuit MI1 ... Microphone SP1, SP ... Speaker SW1 ... Monitor switch B: Door intercom with camera 50 ... Call circuit 51 ... Demodulation circuit 52 ... Carrier level detection circuit 53 ... Speaker amplifier 54 ... Speaker power control means 56 ... Oscillation / modulation circuit 57 ... Frequency demodulation circuit 57a ... Automatic frequency adjustment circuit 57b ... Comparison circuit 58, 59 ... Attenuator circuit 60: Camera circuit 61 ... Camera 70 ... Multiplexing circuit MI2 ... Microphone SP2 ... Speaker SW2 ... Call switch L (L1, L2) ... 2-wire signal line f1 ... first carrier f2 ... second carrier

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 7/18 H04M 9/00

Claims (7)

(57) [Claims] 1. An intercom with a TV installed in a room and a door intercom with a camera installed at a front door are connected, and power is supplied from the intercom with a TV to the intercom with a camera to provide a TV. In a TV intercom system that is equipped with a video and sound monitor function that outputs sound from a speaker at the same time that an image is displayed on the TV of the intercom with a built-in intercom, the first carrier is output to the intercom with a TV when calling, talking, or waiting. , When the monitor switch is operated, the oscillation that stops the output of the first carrier
A modulation circuit is provided, and the door-phone intercom with camera has a carrier level detection circuit for detecting the presence or absence of the first carrier sent from the intercom with television, and this carrier level detection circuit does not detect the first carrier. A television intercom system configured to include a speaker power supply control means for turning off a speaker amplifier when the speaker intercom is turned on. 2. An intercom with a TV installed in a room and a door intercom with a camera installed at a front door are connected to each other, and power is supplied from the intercom with a TV to the intercom with a camera. In a TV intercom system that is equipped with a video and sound monitor function that outputs sound from a speaker at the same time that an image is displayed on the TV of the intercom with a built-in intercom, the first carrier is output to the intercom with a TV when calling, talking, or waiting. , When the monitor switch is operated, an oscillation that generates a different third carrier
A modulation circuit is provided, and a carrier level detection circuit for detecting the presence or absence of a third carrier sent from an intercom with a television is provided in the intercom subunit with a camera, and when the carrier level detection circuit detects the third carrier. A television intercom system including a speaker power supply control means for turning off a speaker amplifier. 3. An intercom with a TV installed in a room and a door intercom with a camera installed at a front door are connected, and power is supplied to the intercom with a camera from the intercom with a TV to provide a TV. In a TV intercom system that is equipped with a video and sound monitor function that outputs sound from a speaker at the same time that an image is displayed on the TV of the intercom with a built-in intercom, the first carrier is output to the intercom with a TV when calling, talking, or waiting. When the monitor switch is operated, an oscillating frequency shift circuit that generates a carrier shifted by a predetermined frequency from the first carrier is provided, and the intercom subunit with camera has a frequency demodulation circuit and an automatic frequency adjustment circuit, A comparison circuit is provided, and the AFC voltage output from this automatic frequency adjustment circuit is used as the comparison circuit. Comparison determination to determine whether the operation of the monitor switch, when it is determined that there operation of the monitor switch is
A television intercom system including a speaker power supply control means for turning off the speaker amplifier. 4. The television intercom system according to claim 1, wherein the intercom with TV has a call after a call switch of a door intercom with camera is operated and power is supplied from the intercom with TV to start a call. The output level switching circuit that increases the output of the oscillation / modulation circuit is further included in the period until the end of the above. The above-mentioned intercom subunit with camera normally attenuates the input sent from the intercom with television. An attenuator circuit and a carrier level detection circuit for detecting the presence or absence of the first carrier are provided. When the carrier level detection circuit detects the first carrier that exceeds a preset threshold value, A television receiver with a configuration that prohibits the attenuation operation by the attenuator circuit at the same time when the speaker amplifier is turned on. Tha phone system. 5. The television intercom system according to claim 4, wherein in the output level switching circuit, a calling switch of a door intercom with camera is operated, power is supplied from the intercom with television, and a predetermined call is started. During the period of, the output of the oscillation / modulation circuit is increased, and when the carrier level detection circuit detects the first carrier that exceeds a preset threshold value, the speaker amplifier is turned on and the attenuator circuit is turned on. A TV intercom system that is configured to prohibit the attenuation operation by. 6. The television intercom system according to claim 1, wherein an attenuator circuit and a carrier level detection circuit are provided in a signal line connecting the intercom with television and the intercom subunit with camera. The circuit is configured so that the attenuation operation is prohibited when the call switch is operated or when the carrier level detection circuit detects the first carrier exceeding a preset threshold value. . 7. The intercom with a TV installed in the room and the intercom subunit with a camera installed at the entrance are 2
The television intercom system according to any one of claims 1 to 6, wherein the television interphone system is configured to be connected by a line signal line, and a video signal is superimposed on a DC power source and transmitted to the two-line signal line.