JP4631498B2 - Video signal transmission direction switching circuit, video control device, signal transmission direction switching device for video control device, and cooperative video signal transmission control system - Google Patents

Description

  The present invention, for example, is incorporated in an interphone master unit of an interphone system with a TV provided in each of two households, and incorporates a video signal transmission direction switching circuit having a function of switching the direction of transmitting a video signal and the like. The present invention relates to a signal transmission direction switching device for a video control device, a cooperative video transmission control system using the same, and a video control device.

  Conventionally, two households have independent TV intercom systems, and interphone master units of systems installed in each household are connected to each other via a transmission line such as a coaxial cable to operate in cooperation. However, in such a linkage system, for example, when the dwelling unit of the parent household is absent, the intercom master unit of the dwelling unit of the child household can respond to the doorphone slave unit with a TV camera, and vice versa. It is possible.

  In such a system, a video signal of a visitor, an audio signal for making a call with the visitor, etc. are transmitted on the transmission path of the intercom master unit between households. Since it differs depending on whether the parent household or child household is set to be away, a video signal transmission direction switching circuit is required at both ends of the transmission path to serve as a buffer for switching and amplifying the video signal transmission direction. It has become.

  Such a video signal transmission direction switching circuit includes an upstream signal amplifier that amplifies an upstream video signal transmitted from each interphone base unit to the transmission path, and a downstream video transmitted from another system to the interphone base unit through the transmission path. There are known downstream signal amplifiers for amplifying signals, and the upstream and downstream signal amplifiers operate mechanical electrical switches such as relays to switch the transmission direction of video signals.

  For example, FIG. 12 shows a basic configuration of a conventional video signal transmission method switching circuit 200, and an upstream signal amplifier 201 and a downstream signal amplifier 202 are interposed between two relays Ry1 and Ry2 in the middle of the transmission path. Are connected in parallel to form upstream and downstream branches L1 and L2, and the relay contacts of the two relays Ry1 and Ry2 are simultaneously switched in one direction (a closed or b closed) to switch the transmission direction. Z0 is an impedance matching resistor.

Note that the following patent document discloses an automatic intercom intercom apparatus in which a noise around the master unit is removed by providing a band-pass filter in a voice switch circuit.
Japanese Patent Laid-Open No. 10-190851

However, since the relay used in such a video signal transmission direction switching circuit is a mechanical electric switch, it is larger in size and higher in cost than other electronic elements.
Therefore, it has been desired to reduce the size and cost of the video signal transmission direction switching circuit by using an electronic element instead of the relay.

The present invention has been made in view of such problems, and its object is to amplify a video signal without using a relay and switch the transmission direction of the video signal. It is an object of the present invention to provide a circuit and a signal transmission direction switching device for video control equipment incorporating the circuit.
Another object is to provide a cooperative video transmission control system incorporating these and a video control device used in the cooperative video transmission control system.

For the above purpose, in claim 1, a video signal transmission direction switching circuit is proposed as a first invention.
Here, the first invention is used in addition to a video control device having a video monitor, is interposed between the video control device and the transmission line, and is input to and output from the video control device through the transmission line. In the video signal transmission direction switching circuit for selectively switching the transmission direction of the video signal, the video signal transmission direction switching circuit is a first signal for amplifying the upstream video signal output from the video control device through the transmission path. An amplifier and a second signal amplifier that amplifies a downstream video signal input to the video control device through the transmission path are connected so that each input terminal is connected to each output terminal. An upstream / downstream video signal amplifier circuit; and a power supply control circuit having an active element that passes power through the first signal amplifier and the second signal amplifier, the active element comprising the video control device Thus on the power supply function, by being off control, the uplink has a configuration which selectively passes downstream video signal.

  According to a second aspect of the present invention, as a second aspect of the invention, it is used in addition to a video control device having a video monitor, interposed between the video control device and the transmission path, and connected to the video control device through the transmission path In the video signal transmission direction switching circuit for selectively switching the transmission direction of the input / output video signal, the video signal transmission direction switching circuit amplifies the upstream video signal output from the video control device through the transmission path. The first signal amplifier and the second signal amplifier that amplifies the downstream video signal input to the video control device through the transmission line are connected so that each input terminal is connected to each output terminal. An up / down video signal amplifier circuit, and a video signal cutoff circuit interposed on the input side of the first and second signal amplifiers. By being controlled passage or blocking of the video signal by the image control apparatus, the uplink has a configuration which selectively passes downstream video signal.

  According to a third aspect of the present invention, in the second aspect, the video signal cutoff circuit includes a ground control active element and a DC cutoff capacitor, and the first control element is controlled by turning on / off the ground control active element. The input side of either one of the second signal amplifiers is grounded / not grounded via the DC blocking capacitor so as to block / pass the video signal.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, the video signal cutoff circuit includes a video signal input active element that selectively inputs a video signal to one of the first and second signal amplifiers, and a power source control. Active element for power supply, and the power supply control active element is turned off / on to stop / supply the drive power to the video signal input active element, thereby blocking / passing the video signal. It is configured.

  According to a fifth aspect of the present invention, in the second aspect, the video signal blocking circuit includes a video signal input active element that selectively inputs a video signal to one of the first and second signal amplifiers, and the video signal. The input side of either the first or second signal amplifier is grounded through the active element for controlling the power supply for cutting off the driving power to the active element for signal input, the direct current interruption capacity, and the direct current interruption capacity. And a ground control active element for blocking the passage of the video signal. The power source active element and the ground control active element are turned off / on and on / off controlled to shut off / It is configured to pass through.

In claim 6, a video control apparatus is proposed as a third invention.
Here, a first signal demultiplexing circuit that multiplexes and separates a video signal, an audio signal, and a control signal transmitted to and from the acoustic image pickup device through a signal line, and a video control device of another system Between a first signal demultiplexing circuit and a second signal demultiplexing circuit that multiplexes and separates a video signal, an audio signal, and a control signal transmitted through a signal line between the first signal demultiplexing circuit and the second signal demultiplexing circuit. The video signal separated by the first signal demultiplexing circuit is allowed or prohibited while the video signal separated by the second signal demultiplexing circuit is blocked from passing. A signal transmission circuit and a video display circuit for processing the video signal separated by the first and second signal demultiplexing circuits and displaying the processed video signal on a video monitor are provided.

Further, in claim 7, as a fourth invention, a signal transmission direction switching device for video control equipment which is preferably used in a cooperative video control transmission system is proposed.
The fourth aspect of the present invention includes the video signal transmission direction switching circuit according to any one of claims 1 to 5 and transmission line voltage monitoring means, wherein the transmission line voltage monitoring means includes a resistance prepared in advance. Is connected to the transmission line to which the voltage detection resistor is connected, and a reference voltage applying means for applying a reference voltage and a voltage of the transmission line generated in the voltage detection resistor when the reference voltage is applied are measured. A voltage measuring circuit, and before outputting the upstream video signal to the transmission line, the reference voltage applying means determines the voltage level detected by the voltage measuring circuit without applying a reference voltage, and the voltage When the level is a predetermined value determined by the application of the reference voltage, the passage of the upstream video signal through the first signal amplifier is prohibited, while the detected voltage level is not the predetermined value. Operates the reference voltage applying means, from application of reference voltage to the transmission line, and to allow passage of the upstream video signal.

In claim 8, as a fifth invention, a cooperative video control transmission system is proposed.
Here, according to a fifth aspect of the present invention, there is provided the video control according to claim 7, wherein each of the two video control devices is connected to the acoustic imaging device and the video control device through a signal line connected to the transmission path. A device signal transmission direction switching device is added, and the video control device signal transmission direction switching devices are further connected to each other via a signal line.

In claim 9, the cooperative video control transmission system in claim 8 is applied to a two-household cooperative television intercom system.
Here, the acoustic imaging device is a door phone device with a camera, the video control device is an interphone master device with a monitor TV, and the signal line is frequency-multiplexed with a video signal, an audio signal, a control signal, a system power supply, etc. It is composed of a two-wire signal line that is transmitted in a superimposed manner by a conversion method.

  According to the present invention, in the video signal transmission direction switching circuit according to the first aspect, transmission of the upstream video signal and the downstream video signal is performed by controlling the active element on and off by the video control device without using a relay. Since the direction is changed, the size can be reduced and the cost can be reduced. In particular, the power supply applied to the first and second signal amplifiers of the upstream / downstream video signal amplifier circuit is blocked to prevent the passage of the video signal, so that there is also an energy saving effect.

  The video signal transmission direction switching circuit according to claim 2 is configured so as to selectively pass the upstream and downstream video signals by using the video signal blocking circuit with the video control device without using a relay. , Downsizing and low cost can be achieved.

  According to the second to fifth aspects of the present invention, the active element for controlling the video signal blocking circuit provided on the input side of the first and second signal amplifiers of the up / down video signal amplifier circuit is controlled to be turned on / off. At least one video signal is blocked from passing, and the transmission direction of the upstream video signal and the downstream video signal is switched.

  Further, in this configuration, when the active element for controlling the video signal cut-off circuit is on / off-controlled, the first and second signal amplifiers on the output side can be set in the operating state / non-operating state, so that reception is possible. This eliminates the need for an impedance matching resistor on the side and eliminates the loss caused by the voltage division between the impedance matching resistor on the transmitting side and the impedance matching resistor on the receiving side, thus eliminating the need to increase the gain of the upstream signal amplifier. Therefore, the cost can be further reduced.

  According to the video control device of claim 6, when the one-way video signal transmission circuit is not provided, the input impedance of the video signal when viewed from the other system is the input impedance of the acoustic image pickup device and the input of the video display circuit. When the video signal is transmitted from the video control device of the other system in order to eliminate the problem that the video is disturbed due to the impedance mismatch caused by this impedance mismatch, By making the video signal transmission circuit function, it is not necessary to consider the input impedance of the acoustic image pickup device, thereby preventing impedance mismatching and receiving a good video.

  8. The signal transmission direction switching device for video control equipment according to claim 7, wherein the video signal transmission direction switching circuit transmits the video signal to the other system side connected by a signal line so as to cooperate with each other before transmitting the video signal. Thus, since it is determined whether or not the video signal is transmitted from another system, it is possible to prevent the occurrence of a communication problem in which the video signal collides on the transmission path.

  Further, the signal transmission direction switching device for a video control device having such a configuration can be used as an external optional device attached to the video control device constituting the interphone master unit or the like.

  According to claim 8, the signal transmission direction switching device for a video control device according to claim 7 is provided for each of two independent video signal transmission control systems configured by combining an image pickup device and a video control device. Can be configured simply by incorporating. Therefore, the existing video signal transmission control system can be developed as a cooperative system without changing the internal configuration of the video control device.

  According to the ninth aspect, the existing television intercom system can be effectively used as it is simply by incorporating the video control device signal transmission direction switching device according to the seventh aspect without changing the internal configuration of the video control device. A two-wire two-household TV intercom system can be easily realized.

  Examples of the present invention will be described below.

  1 is a video signal transmission direction switching circuit proposed as the first invention, FIG. 2 is a cooperative video signal transmission control system incorporating the video signal transmission direction switching circuit, and FIG. 3 is a basic configuration of a video control device. FIG.

  As shown in FIG. 2, the cooperative video signal transmission control system is configured by connecting the first system S1 and the second system S2 having the same configuration with a two-wire signal line L. ing.

As shown in FIG. 2, each of the systems S <b> 1 and S <b> 2 connects the acoustic image pickup device 5 and the video control device 2 with a signal line L, and each video control device 2 has a video signal transmission direction. The switching circuit 1, the bidirectional signal transmission circuit 4, and a pair of signal multiplexing / demultiplexing circuits 3 and 3 are connected to the two-wire system cooperation compatible adapter 6 via the signal line L.
Here, a set of signal multiplexing / demultiplexing circuits 3 multiplex an audio signal used for a call, a video signal for video display, and a control signal for controlling the system by using a frequency multiplexing system. And separated.

  The cooperative system shown in FIG. 2 can be representatively applied as a two-household cooperative TV interphone system. In this case, the acoustic image pickup device 5 is a door phone with a camera, a video control device 2, and a two-wire system. Although the intercom base unit with the monitor television is applied to the cooperation-compatible adapter 6, it is not limited thereto. The two-wire system cooperation compatible adapter 6 does not have to be a separate body from the video control device 2 and may be incorporated in the same casing.

FIG. 1 shows a video signal transmission direction switching circuit according to the first aspect of the present invention.
The transmission direction switching circuit 1 is input to the video control device 2 side through the transmission line L from the first signal amplifier 11a that amplifies the upstream video signal output from the video control device 2 through the transmission line Lo. The upstream / downstream video signal amplifying circuit 11 is configured by connecting the second signal amplifier 11b for amplifying the downstream video signal so that the respective input terminals are connected to the respective output terminals. Power is supplied to the first signal amplifier 11a and the second signal amplifier 11b by power control circuits 12 and 12 having active elements 12a and 12b. Note that C is a DC blocking capacitor that allows a video signal to pass and blocks a DC signal, and ZS1 and Zr1 are impedance matching resistors provided to prevent signal reflection by the transmission path. Here, with respect to the video signal, the equivalent impedance value of the video signal transmission direction switching circuit 1 as viewed from the signal demultiplexing circuit 3 is the same as when the video signal is sent from the video signal transmission direction switching circuit 1 to the signal demultiplexing circuit 3. It is desirable that the value be unchanged when the video signal is sent from the separation circuit 3 to the video signal transmission direction switching circuit 1. Therefore, when a video signal is sent from the video signal transmission direction switching circuit 1 to the signal demultiplexing circuit 3, the impedance value (ZS1) of the impedance matching resistor ZS1 that dominates the equivalent impedance value of the video signal transmission direction switching circuit 1 and When the video signal is sent from the signal demultiplexing circuit 3 to the video signal transmission direction switching circuit 1, the impedance matching resistor ZS1 and the impedance matching resistor Zr1 that govern the equivalent impedance value of the video signal transmission direction switching circuit 1 The impedance value (ZS1) and the impedance of the impedance matching resistor ZS1 are established so that the condition (ZS1) ≈ (ZS1 // Zr1) is satisfied so that the parallel composite impedance value (ZS1 // Zr1) becomes a substantially close value. Determines two values of impedance value (Zr1) of matching resistor Zr1 There is a need.

  Here, the first and second signal amplifiers 11a and 11b receive the control signals sent from the video control device 2 by the active elements 12a and 12b provided in the corresponding power control circuits 12 and 12, respectively. The signal amplifier that is turned on and off and thus supplied with power passes the video signal, and the signal amplifier that is turned off shuts off the video signal so that the upstream and downstream video signals are transmitted. Pass through selectively.

  In the configuration of FIGS. 1 and 2, the control signals sent from the video control devices 2 and 2 of the two systems S 1 and S 2 connected by the signal line L are sent to the bidirectional control built in the adapter 6. The signal is transmitted to another system via the signal transmission circuit 4. In addition to the signal line L, a transmission line for connecting the video control device 2 and the signal demultiplexing circuit 3 is also used, and this transmission line is not connected via the signal terminal T2, but is connected to the connector C1 provided in the video control device 2. And the video control device 2 and the signal demultiplexing circuit 3 are connected through a pair of connectors C1 and C2 which are paired with a connector C2 provided in the two-wire system cooperation compatible adapter 6. Further, by supplying / stopping the above-described power supply by the power supply and the signal from the video control device 2 via the pair of connectors C1 and C2, the upstream video signal and the downstream video signal can be alternatively passed. Control is being made.

  For example, when a two-household intercom system is configured with the configuration of FIG. 2, when both systems S 1 and S 2 are operated independently, the video control device 2 is connected to any of the power control circuits 12, 12, the video signal transmission direction switching circuit 1 does not pass the upstream video signal and the downstream video signal, and therefore the reception of the video signal from the other system S2 is also blocked. When one of the systems S1 and S2 is set for a cooperative operation, for example, an absence setting is made in the intercom system, the video signal transmission direction switching circuit 1 added to the video control device 2 of the system S1 transmits the upstream video signal. Passing is permitted, and an absence setting request is sent to the video control device 2 of the other system S2.

  As a result, in the system S1, power is supplied by the power control circuit 12 corresponding to the first signal amplifier 11a, and in the system S2, the power supply corresponding to the second signal amplifier 11b is received from the video control device 2 Only the control circuit 12 supplies power and permits the passage of the downstream video signal, so that the video signal received from the acoustic image pickup device 5 by the video control device 2 on the system side set for absence is used as the other system. The video control device can respond, respond, and respond.

  For example, when the system constitutes a two-household TV intercom, when a visitor calls and operates the doorphone slave unit of the household system set to absence, the intercom master unit of the system of the other household linked to this You can answer and talk while watching visitors.

  FIG. 3 is a block diagram showing the internal configuration of the video control device applied to the TV intercom system. As shown in FIG. 2, the signal terminal T1 is connected to the acoustic image pickup device 5 through the signal line L. The signal terminal T2 is connected to another system through the two-wire system cooperation compatible adapter 6 and the signal line L.

  The video control device 2 includes a call circuit 21 having a microphone MC for a call, a speaker SP, a video display circuit 22 for processing a video signal of a visitor transmitted from the acoustic image pickup device 5, and a CRT for displaying a video of the visitor. In addition to the video monitor 22a constituted by a liquid crystal screen or the like, a control circuit 26 constituted by a first signal demultiplexing circuit 23, a second signal demultiplexing circuit 24, a control signal transmitting / receiving circuit 25, a CPU, etc. A power circuit 27 for supplying power to each unit is provided.

  Here, the first signal demultiplexing circuit 23 converts the multiplexed signal sent from the acoustic image pickup device 5 into a camera-equipped doorphone child drive power source, a sound signal, a control signal including a calling signal, an image, and the like. The signals are separated and multiplexed, and sent to the acoustic image pickup device 5.

  The second signal demultiplexing circuit 24 separates a multiplexed signal transmitted from another system into a control signal and a video signal including a voice signal, a calling signal, and multiplexes these signals. Sending to other system side. These are easily configured by a known technique such as a bandpass filter.

  The control signal transmission / reception circuit 25 sends various control signals generated by operating an operation unit (not shown) to the first signal demultiplexing circuit 23 and the second signal demultiplexing circuit 24 for multiplexing. Further, the control signal transmitted from the acoustic image pickup device 5 or another system in the form of a multiplexed signal and separated by the first signal demultiplexing circuit 23 and the second signal demultiplexing circuit 24 is received.

Next, a video signal transmission direction switching circuit according to the second aspect of the present invention will be described.
FIG. 4 shows the basic configuration of the video signal transmission direction switching circuit according to the second aspect of the present invention, and FIGS. 5 to 7 show specific examples of the video signal cutoff circuit.

  The transmission direction switching circuit 1A includes a first signal amplifier 11a that amplifies the upstream video signal output from the video control device 2 through the transmission line Lo, and the video control device 2 side from the other system through the signal line L and the transmission line Lo. The upstream / downstream video signal amplifier circuit 11 is configured by connecting the second signal amplifier 11b for amplifying the downstream video signal input to the input terminal so that each input terminal is connected to each output terminal. Video signal cut-off circuits 13 and 13 are provided on the input side of the first signal amplifier 11a and the second signal amplifier 11b. C is a DC blocking capacitor that allows a video signal to pass and blocks a DC signal, and ZS2 is an impedance matching resistor provided to prevent reflection of the video signal on the transmission line Lo.

  Here, the video signal blocking circuits 13 and 13 are provided with active elements 13a and 13a which are controlled to be turned on and off in response to a control signal sent from the video control device 2, and these active elements 13a and 13a are provided. By performing on / off control, upstream and downstream video signals are selectively passed. That is, in this circuit, when a control signal is sent from the video control device 2 to any one of the video signal blocking circuits 13 and 13, the signal blocking circuits 13 and 13 directly block the passage of the upstream and downstream video signals. ing.

  That is, in the transmission direction switching circuit 1A, the first signal amplifier 11a does not cut off the power supply and outputs and holds a constant voltage level when the video signal is not passed. It is not necessary to provide a receiving impedance matching resistor corresponding to the side impedance matching resistor Zr1 (see FIG. 1). Further, since such impedance matching resistor Zr1 is not provided, there is no loss due to voltage division of the output from the signal amplifier, so that it is not necessary to set the gain of the signal amplifier large.

  Next, a specific example of the signal cutoff circuit 13 will be described. In the following, an example is shown in which both are provided on the input side of a signal amplifier (corresponding to the first and second signal amplifiers 11a and 11b), and Q3, Q5 are used as the control active element 13a by the control signal. Is turned on and off to prohibit the input of the video signal to the signal amplifier.

  The video signal cut-off circuit 13A shown in FIG. 5 is provided on the input side of the signal amplifier and includes a control active element Q3 that grounds the transmission line Lo via the capacitor C1, but does not include a relay element. .

Here, the control active element Q3 is composed of a transistor, and when a base current is supplied to the base from the video control device 2, the transmission line Lo is grounded through the capacitor C1, so that the video signal flows into the ground through the capacitor C1. It is configured to be blocked by.

  In this example, a resistance built-in transistor element is employed as the control active element Q3, but a configuration using a field effect transistor element or the like is also possible.

  The video signal cut-off circuit 13B shown in FIG. 6 is configured to cut off the drive power supplied to the signal input active element Q4 by the control active element Q5 that is on / off controlled by the video control device 2. Does not include relay elements.

Here, the signal input active element Q4 constitutes an emitter follower circuit of a transistor element, and a resistor element and DC blocking capacitors C2 and C3 are connected to the emitter follower circuit as shown in FIG. The base of the transistor element is connected to the transmission line Lo, and a video signal is input. That is, in this example, a resistor is provided at the emitter of the transistor element Q4, and further input to the signal amplifier through the capacitor C3.

Further, although transistor elements are used as the signal input active element Q4 and the control active element Q5, a configuration using a field effect transistor element or the like is also possible instead.

  The video signal cut-off circuit 13C shown in FIG. 7 is obtained by adding the configuration of FIG. 6 to the configuration of FIG. 5, and the video control device 2 turns off the control active element Q5 and turns on the control active element Q3. Thus, the video signal applied to the transmission line Lo is blocked from being input to the signal amplifier.

  If the video signal transmission direction switching circuit 1A is configured using the video signal cutoff circuit 13 as described above, the first and second signal amplifiers 11a and 11b only block the video signal without shutting off the power supply. Thus, it is possible to allow or block the passage of either the upstream video signal or the downstream video signal.

  That is, in the transmission direction switching circuit 1A, the power supply of the first and second signal amplifiers 11a and 11b is not cut off and is held at a constant voltage level when the video signal is not passed. Therefore, since the output impedance from the signal amplifier does not have a loss due to voltage division, it is not necessary to set a large gain of the signal amplifier to compensate for the loss due to voltage division.

Next, video control equipment used in the cooperative video signal transmission control system will be described.
The video control device 2A is characterized in that the configuration shown in FIG. 3 includes a one-way video signal transmission circuit 28.

  That is, the video control device 2A includes a microphone MC for a call, a call circuit 21 having a speaker SP, a video display circuit 22 for processing a video signal to display a video of a visitor, a CRT, a liquid crystal screen, and the like. In addition to the video monitor 22a, the first signal demultiplexing circuit 23, the second signal demultiplexing circuit 24, the control signal transmitting / receiving circuit 25, the control means 26 composed of a CPU, etc. A circuit 27 is provided.

Here, the first signal demultiplexing circuit 23 converts the multiplexed signal sent from the acoustic image pickup device 5 into a camera-equipped doorphone child drive power source, a sound signal, a control signal including a calling signal, an image, and the like. The signals are separated and multiplexed, and sent to the acoustic image pickup device 5.
The second signal demultiplexing circuit 24 separates a multiplexed signal transmitted from another system into a control signal and a video signal including a voice signal, a calling signal, and multiplexes these signals. Sending to other systems.

  The unidirectional video signal transmission circuit 28 allows the video signal separated by the first signal demultiplexing circuit 23 to enter the video display circuit 22, but transmits it from the partner system connected by the signal line L. The video signal separated by the second signal separation circuit 24 is further reflected from the acoustic image pickup device 5 through the first signal separation circuit 23, and then enters the video display circuit 22 to be displayed on the video monitor 22a. In such a configuration, even when a cooperative system is configured, it is possible to display a clear image with no image disturbance on the video monitor 28a. Become.

  The control signal transmission / reception circuit 25 sends various control signals generated by operating an operation unit (not shown) to the first signal demultiplexing circuit 23 and the second signal demultiplexing circuit 24 for multiplexing. The control signal transmitted from the acoustic image pickup device 5 and other systems in the form of multiplexed signals and separated by the first signal demultiplexing circuit 23 and the second signal demultiplexing circuit 24 is received.

Next, a signal transmission direction switching device for video control equipment used when configuring a cooperative system will be described.
This signal transmission direction switching device 1B includes a transmission line voltage monitoring means 7 in order to ensure cooperation between the video signal transmission direction switching circuit 1 or 1A described above and the counterpart system, and is a system that cooperates with each other. Used in each of S1 and S2.

  Here, the transmission line voltage monitoring means 7 includes a reference voltage applying means 71 having an active element Q6 for applying a reference voltage Vref by adding a resistor R1 to the transmission line Lo, and a voltage connected to the transmission line Lo. A voltage measuring circuit 72 that detects a voltage level Vx generated in the detection resistor R2, and the video control device 2 applies the reference voltage Vref by the reference voltage applying means 71 before outputting the video signal to the transmission line Lo. The voltage level Vx generated in the transmission line Lo is discriminated with reference to the voltage measuring circuit 72 in a state where the voltage level is not determined, and the voltage level Vx is determined to be a predetermined value determined when the reference voltage application means 71 applies the reference voltage Vref to the transmission line Lo When it is not V1, the active element Q6 of the reference voltage applying means 71 is turned on to apply the reference voltage Vref to the transmission line Lo, and then send the video signal. , When the voltage level Vx of the transmission line Lo is a predetermined value V1, by prohibiting the transmission of the video signal, so as not to collide with video signals respectively sent from one system to work. That is, the transmission line voltage monitoring means 7 prevents collision of video signals between systems that cooperate on the basis of the following principle.

FIG. 10 illustrates the basic operation of the reference voltage applying means 71 and the discrimination principle.
FIG. 10A shows a state where both systems stop sending video signals, FIG. 10B shows a state where one system is sending or preparing to send video signals, and FIG. c) shows a state where both systems are ready to send.

  In FIG. 10, Vx represents a voltage level generated in the transmission line Lo, Vo represents a voltage level generated when the reference voltage Vref is not applied to the transmission line Lo (the transmission line Lo is composed of capacitors C and C). Since the DC component is cut off, the value is almost zero in a normal state).

From these figures, when one system measures the voltage level Vx of the transmission line Lo and when the other system pauses the transmission of the video signal (standby), the voltage level Vx of the transmission line Lo is When one system measures the voltage level Vx of the transmission line, and the other system is sending a video signal or is preparing to send (in operation), the transmission line Lo The voltage level Vx is approximately (R2 / 2) / [R1 + R2 / 2] · Vref = V1, and when one system is preparing a video signal and the other system is preparing to send, The voltage level Vx of Lo is
Since R2 / (R1 + R2) · Vref = V2, the video signal collision can be prevented by measuring and determining the voltage level Vx of the transmission line Lo by the voltage measuring circuit 72 before sending the video signal. .

  Steps 101 to 111 in FIG. 11 show the discrimination operation in the video control device on the video signal sending side.

  When there is a video command for the video signal, the voltage measurement circuit 72 is referred to measure the voltage level Vx of the transmission line Lo. As a result of the measurement, in the case of FIG. 10A, that is, when it is Vo, it is determined that the counterpart system is on standby, and the reference voltage Vref is applied to the transmission line Lo to be ready for transmission. In the case of FIG. 10B, it is determined that the counterpart system is operating, and transmission is prohibited (steps 102 to 106, 103 to 104).

In step 107, the voltage level Vx of the transmission line Lo is referenced again.
As a result, in the case of the value V1 in the case of FIG. 10A, it is determined that the counterpart system is in a standby state, and the video signal is transmitted, but the value V2 in the case of FIG. If there is, it is determined that the other system is operating and transmission is prohibited (steps 107 to 111). Since the own system also closes the element Q6 during preparation for transmission, the voltage level Vx does not become the value Vo, and it is clear that the other system is on standby in the case of the value V1.

Finally, an example of application to a cooperative intercom system with a TV for two-family dwelling units will be described.
For example, if the intercom master unit with a monitor TV in the parent household unit is set to the absence state, if a visitor calls from the door phone slave unit with a TV camera at the entrance of the parent household unit, the parent household unit The video signal transmission direction switching device added to the monitor TV interphone master unit measures the voltage on the transmission line and determines whether the interphone master unit in the child household side unit is sending video signals or preparing for transmission. If not, otherwise, the video signal transmitted from the intercom unit is sent to the interphone base unit of the child household side dwelling unit.

  In the interphone master unit of the child household side unit, the video signal transmission direction switching device is set to a state in which the video signal can be received when the absence setting signal is received from the parent household side unit. It is displayed on the video monitor of the interphone master unit of the child household side unit, and in response to the call of the visitor of the door phone slave unit, it is possible to make a call while watching the video of the visitor.

  If the interphone master unit of the child household side dwelling unit is transmitting or preparing for transmission of the video signal, transmission of the video signal is stopped and the video signal transmission direction switching device accepts the video signal.

If the intercom master unit with a monitor TV in the child household is set to absence,
The intercom master unit with a monitor TV in the parent household unit responds to the visitor and makes a call while watching the visitor's video.

The block diagram which shows the basic composition of the video signal transmission direction switching circuit by 1st invention. The block diagram which shows the basic composition of a cooperation type video signal transmission control system. The block diagram which shows the basic composition of a video control apparatus. The block diagram which shows the basic composition of the video signal transmission direction switching circuit by 2nd invention. The circuit diagram which shows an example of a video signal cutoff circuit. The circuit diagram which shows another example of a video signal interruption | blocking circuit. The circuit diagram which shows another example of a video signal cutoff circuit. The block diagram which shows the basic composition of the video control apparatus by 3rd invention used for a cooperation type video signal transmission control system. The block diagram which shows the signal transmission direction switching apparatus for video control apparatuses by 4th invention. The figure explaining the transmission collision prevention principle of a video signal in a cooperation type video signal transmission control system. The flowchart explaining the collision prevention operation | movement of the video signal in a cooperation type video signal transmission control system. The figure which shows the conventional video signal transmission direction switching circuit

Explanation of symbols

1, 1A Video signal transmission direction switching circuit 2, 2A Video control device 5 Acoustic image pickup device 11 Up / down signal amplification circuit 11a, 11b First and second signal amplifier 12 Power supply control circuit 12a, 12b Active element 13, 13A , 13B, 13C Signal cut-off circuit 13a Control active element 7A Video control device signal transmission direction switching device 7 Transmission line voltage monitoring means 71 Reference voltage applying means 72 Voltage measurement circuit Vref Reference voltage Lo Transmission line L Signal lines Q3, Q5 Active Elements 22, 23 First and second signal demultiplexing circuit 22a Video monitor 28 Unidirectional video signal transmission circuit

Claims (9)

Used in addition to video control equipment with a video monitor, interposed between the video control equipment and the transmission line, and selectively enters the transmission direction of the video signal that enters and outputs through the transmission line. In the video signal transmission direction switching circuit to switch to
The video signal transmission direction switching circuit is
A first signal amplifier that amplifies an upstream video signal output from the video control device through the transmission line; and a second signal amplifier that amplifies a downstream video signal input to the video control device through the transmission line. An upstream / downstream video signal amplifying circuit configured such that each input terminal is connected to each output terminal;
A power control circuit having an active element that passes power through the first signal amplifier and the second signal amplifier;
The active element is a video signal transmission direction switching circuit configured to selectively pass the upstream and downstream video signals when the power supply function is on / off controlled by the video control device. Used in addition to video control equipment with a video monitor, interposed between the video control equipment and the transmission line, and selectively enters the transmission direction of the video signal that enters and outputs through the transmission line. In the video signal transmission direction switching circuit to switch to
The video signal transmission direction switching circuit is
A first signal amplifier that amplifies an upstream video signal output from the video control device through the transmission line; and a second signal amplifier that amplifies a downstream video signal input to the video control device through the transmission line. The input / output terminals of the upstream / downstream video signal amplifier circuit and the first and second signal amplifiers, each of which is connected so that each input terminal is connected to each output terminal. A signal cut-off circuit,
The video signal cut-off circuit is a video signal transmission direction switching circuit configured to selectively pass the upstream and downstream video signals when the video control device controls passage or blocking of the video signals. In claim 2,
The video signal cutoff circuit includes a ground control active element and a DC cutoff capacitor,
By controlling on / off of the ground control active element, the video signal is stopped by grounding / not grounding the input side of either the first or second signal amplifier via the DC blocking capacitor. / Video signal transmission direction switching circuit configured to be supplied. In claim 2,
The video signal cut-off circuit includes a video signal input active element for selectively inputting a video signal to one of the first and second signal amplifiers, and a power control active element.
A video signal transmission direction switching circuit configured to stop / supply driving power to the video signal input active element by shutting off / passing the video signal by controlling off / on of the power control active element. . In claim 2,
The video signal cut-off circuit includes a video signal input active element for selectively inputting a video signal to one of the first and second signal amplifiers, and a drive power supply to the video signal input active element. An active element for controlling the power supply to be cut off, a DC blocking capacitor, and a ground for blocking the passage of the video signal by grounding one of the input sides of the first and second signal amplifiers through the DC blocking capacitor. An active element for control,
A video signal transmission direction switching circuit configured to block / pass a video signal by controlling off / on and on / off control of the power supply active element and the ground control active element. A first signal demultiplexing circuit that multiplexes and separates a video signal, an audio signal, and a control signal that are transmitted to and from the acoustic image pickup device through a signal line;
A second signal demultiplexing circuit that multiplexes and separates a video signal, an audio signal, and a control signal transmitted through a signal line with a video control device of another system;
The video signal interposed between the first and second signal demultiplexing circuits and separated by the first signal demultiplexing circuit is allowed to pass while being separated by the second signal demultiplexing circuit. A one-way video signal transmission circuit that blocks the passing video signal,
A video control device comprising: a video display circuit that processes the video signal separated by the first and second signal demultiplexing circuits and displays the video signal on a video monitor. The video signal transmission direction switching circuit according to any one of claims 1 to 5, and a transmission line voltage monitoring means,
The transmission line voltage monitoring means includes:
A resistance prepared in advance is connected to the transmission line to which the voltage detection resistor is connected, and a reference voltage applying means for applying a reference voltage, and the transmission line generated in the voltage detection resistor when the reference voltage is applied. With a voltage measurement circuit that measures the voltage,
Before outputting the upstream video signal to the transmission line, the reference voltage applying means determines the voltage level detected by the voltage measuring circuit in a state where no reference voltage is applied, and the voltage level is determined by the reference voltage application. When the value is a value, the passage of the upstream video signal through the first signal amplifier is prohibited. On the other hand, when the detected voltage level is not the predetermined value, the reference voltage applying means is operated to connect the reference voltage to the transmission line. A signal transmission direction switching device for video control equipment that permits passage of the upstream video signal after application of.   The signal transmission direction switching device for a video control device according to claim 7 is added to each of the two video control devices respectively connected to the acoustic imaging device and the video control device through a signal line leading to the transmission path. A cooperative video signal transmission control system configured by connecting the signal transmission direction switching devices for the video control equipment via signal lines. 9. The acoustic imaging device according to claim 8, wherein the acoustic imaging device is a door phone device with a camera, the video control device is an interphone master device with a monitor television, and the signal line includes a video signal, an audio signal, a control signal, a system power supply, and the like. A collaborative video signal transmission control system comprising a two-wire signal line that is superimposed and transmitted by a frequency multiplexing method and constituting a two-household collaborative television intercom system.

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