JPH11313312A - Video interphone device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the degree of freedom of wiring by terminating a television monitor terminal with a characteristic impedance of a trunk line to reduce multi-reflection. SOLUTION: This video interphone device connects plural television monitor terminals 2a, 2b, 2c, 2d, 2e, 2f onto trunk lines L1, L2, L3, L4, L5 through which a video signal S1 is transmitted, the plural television monitor terminals 2a, 2b, 2c, 2d, 2e, 2f are respectively terminated by a characteristic impedance Z0 of the trunk lines L1, L2, L3, L4, L5 to reduce multi-reflection, to transmit the video signal and to attain wiring freely. The television monitor terminals 2a, 2b, 2c, 2d, 2e, 2f respectively have trunk line amplifiers 23a, 23b, 23c, 23d, 23e, 23f that amplify the video signal in the television monitor terminals and send the amplified signal as signal generating sources 24a, 24b, 24c, 24d, 24e, 24f with an output impedance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television intercom apparatus, and more particularly, to a television intercom apparatus for connecting a plurality of television monitor terminals.
The present invention relates to a television intercom apparatus that can be connected to a main line with free wiring without using a distributor or the like.

[0002]

2. Description of the Related Art Conventionally, a television intercom apparatus shown in a system configuration diagram of FIG. 6 has been proposed as this kind of television intercom apparatus. The video intercom apparatus shown in FIG. 1 is installed at the entrance of a dwelling unit having multiple floors (here, the first floor, the second floor, and the third floor) (a dwelling unit entrance), and captures an image near the dwelling unit entrance. A camera-equipped entrance slave unit 51 provided with a calling function for calling a resident in the dwelling unit by a visitor and the like and a communication function with the resident, and a camera-equipped entrance slave unit 51 installed on each floor in the dwelling unit. TV monitor terminals 52a, 52b, 52c, 52d, and 52e having a video playback function for displaying captured video and the like, and TV monitor terminals 52a, 52b, 52c, 52d, and 52
e, an intercom terminal 5 having a call answering function for responding to a call from a visitor or the like using the camera-equipped entrance slave unit 51 and a call function with the visitor or the like.
3a, 53b, 53c, 53d and 53e.

Here, on the second floor of the above-mentioned dwelling unit shown in the system configuration diagram of FIG. 6, a television monitor terminal 52a and an intercom terminal 53a to which a camera-equipped entrance device 51 is connected via a transmission line are provided. On the third floor, TV monitor terminals 52b and 52c and intercom terminals 53b and 53
c, on the first floor of the dwelling unit, TV monitor terminals 52d, 52e
And intercom terminals 53d and 53e are respectively installed. The TV monitor terminals 52a installed on the second floor of the dwelling units are TV monitor terminals 52b, 5
They are connected by trunk lines in the order of 2c, 52d, and 52e. Similarly, the intercom terminal 53a installed on the second floor of the dwelling unit is connected to the intercom terminals 53b and 53e by a trunk line, the intercom terminal 53b is connected to the intercom terminal 53c, the intercom terminal 53e is connected to the intercom terminal 53d by the trunk line, respectively. ing.

[0004] FIG. 7 is a front view of a camera-equipped entrance device 51 and a plurality of television monitor terminals 52 shown in the system configuration diagram of FIG.
It is a block diagram which shows the circuit structure of 52a, 52b, 52c, 52d, and 52e. As shown in the figure, of the plurality of television monitor terminals 52a, 52b, 52c, 52d, 52e, the video signal S51 output from the camera-equipped entrance device 51.
Except for the television monitor terminal 52e installed on the first floor of the dwelling unit having the terminal function of
Hereinafter, the configuration of the television monitor terminal 52a to which the camera-equipped entrance device 51 is connected via the transmission path and the configuration of the television monitor terminal 52e having the terminal function will be described, and the configuration of the other television monitor terminals 52b, 52c, and 52d. Is omitted.

[0005] The television monitor terminal 52a converts the video signal S51 output from the camera-equipped entrance device 51 via the transmission path into a video signal S51.
A branching unit 60a for branching and transmitting to the own terminal (52a) and a television monitor terminal 52b to be transmitted later, and an amplifier 61a for amplifying the video signal S51 via the branching unit 60a
And a television monitor 62a for reproducing the video signal S51 via the amplifier 61a. In addition, the television monitor terminal 52e having a terminating function is provided in addition to the components of the above-described television monitor terminal 52a, for matching the impedance for operating the splitter 60e normally, and connected to the reference potential point. The termination resistor 63e is provided.

Further, each of the television monitor terminals 52a, 52
b, 52c, 52d, 52e branching devices 60a, 60b,
60c, 60d, 60e and amplifiers 61a, 61b, 6
1c, 61d and 61e are connected over a short distance in order to reduce multi-reflection of the video signal S51. In the television intercom apparatus configured as described above, the video signal S51 on which the audio signal captured by the camera-equipped entrance device 51 is superimposed is transmitted to the television monitor terminal 52a installed on the second floor of the dwelling unit via the transmission path. Is entered. This video signal S
The television monitor terminal 52a that has received 51 receives the audio signal of the audio component and the video signal of the video component, and sends the audio signal to the intercom terminal 53a that is installed adjacently. It is input to the branching unit 60a of the television monitor terminal 52a shown in the block diagram. In addition, the audio signal of the audio component input to the above-mentioned intercom terminal 53a is transmitted to each of the intercom terminals 53b, 53c,
A description of a method (means) for transmitting to 53d and 53e is omitted.

[0007] The branch unit 60a of the television monitor terminal 52a
Branches the input video signal S51, while one
1a and sends the amplified video signal S51 to the television monitor 6
2a, and the other is transmitted to the television monitor terminal 52b installed on the third floor of the dwelling unit via the main line.
The video signal S51 input to the TV monitor terminal 52b is
Similarly to the above-described television monitor terminal 52a, the signal is branched by the branching unit 60b, amplified by the amplifier 60b, reproduced by the television monitor 61b, and transmitted to the television monitor terminal 52c via the main line. Therefore, the video signal S51 input to the television monitor terminal 52c is also subjected to signal processing in the same manner as the above-described television monitor terminals 52a and 52b, and is transmitted in the order of the television monitor terminals 52d and 52e.
It is reproduced on each of the television monitors 61c, 61d, 61e.

[0008]

However, since the conventional TV intercom apparatus is configured as described above, it is necessary to keep the impedance as viewed from the input / output side of each TV monitor terminal constant at all times. Impedance mismatching occurs, and a standing wave is generated from a reflected wave due to multi-reflection, resulting in an increase in loss, a passband becoming unstable, and a malfunction of the branching device.

Therefore, as shown in the block diagram of FIG. 8, a television monitor terminal 52c installed on the third floor of a dwelling unit has
A terminal resistor 63c for terminating the video signal S51 is added, and the television monitor terminal 52b and the television monitor terminal 5 are added.
2c and the TV monitor terminal 52d are connected in parallel (parallel) so that the impedance is halved, so that the video reproduced by the TV monitors 62c, 62d and 62e of the TV monitor terminals 52c, 52d and 52e can be reproduced. Each intercom terminal 53a, 53, which will not be described in detail,
As shown in the system configuration diagram of FIG. 6, it is difficult to perform long-distance wiring such as a trunk used for a transmission line of a low-frequency intercom system audio signal transmitted between b, 53c, 53d, and 53e. Each TV monitor terminal 52a, 52b, 5
The trunk line, which is the transmission path of the video signal S51 transmitted between the 2c, 52d, and 52e, requires the use of a crossover wiring (sending wiring). First, wiring is performed from the second floor to the third floor of the dwelling unit, and wiring is performed again through the second floor to the first floor. Therefore, there is a problem that the construction cost at the time of installation of the television intercom apparatus or the like increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned difficulties, and outputs a video signal with a characteristic impedance of a main line and terminates a plurality of television monitor terminals connected via the main line with the characteristic impedance of the main line. (Reception), it is possible to reliably reduce multi-reflection of video signals, reproduce good video on a TV monitor, and improve the degree of freedom of wiring for connecting a plurality of TV monitor terminals. It is intended to provide a device.

[0011]

In order to achieve the above object, a television intercom apparatus according to the present invention is a television intercom apparatus for connecting a plurality of television monitor terminals on a main line for transmitting a video signal. Multi-reflection by terminating each TV monitor terminal with the characteristic impedance of the main line, transmitting video signals,
This allows free wiring.

[0012] The television monitor terminal has a main line amplifier which amplifies the video signal in the television monitor terminal and sends it out again as a signal generation source with an output impedance. According to such a television intercom apparatus, the input impedance of the video signal transmitted to the plurality of television monitor terminals is received by the terminating resistor of the characteristic impedance of the main line, and is amplified by the characteristic impedance (output impedance) of the main line. By outputting the signal from the signal source of the amplifier, it is possible to eliminate the cause of multi-reflection of the transmitted video signal and to connect a plurality of television monitor terminals via a trunk line to a trunk amplifier provided in any television monitor terminal. It is possible to improve the degree of freedom of wiring without using a branching / distributing device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment to which a television intercom apparatus according to the present invention is applied will be described below as an embodiment with reference to the drawings. The TV intercom apparatus shown in the system configuration diagram of FIG. 1 is installed at the entrance of a dwelling unit (a dwelling unit entrance) having a plurality of floors (not shown), a video imaging function for capturing an image of the vicinity of the dwelling unit, and the inside of the dwelling unit by visitors and the like Camera-equipped entrance device 1 having a calling function for calling a resident and a communication function with the occupant, and a video playback device installed in the dwelling unit and displaying an image taken by the camera-equipped entrance device 1 A plurality of television monitor terminals 2a, 2b, 2c, 2d, 2e, 2f having functions and the like, and a camera-equipped entrance device 1 installed adjacent to the television monitor terminals 2a, 2b, 2c, 2d, 2e, 2f; Terminals 3a, 3b, 3c, 3 provided with a call answering function for responding to a call from a visitor or the like using
d, 3e and 3f. The intercom terminals 3a, 3b, 3c, 3d, 3e, and 3f are connected (wired) by a trunk line (not shown) and have an extension call function that enables a call between the intercom terminals.

The television monitor terminals 2b and 2c are connected to the television monitor terminal 2a to which the camera-equipped entrance device 1 is connected via the transmission line L0 via (two-wire) trunk lines L1 and L2, respectively. The television monitor terminal 2b is connected to the television monitor terminals 2d and 2e via trunk lines L3 and L4, and the television monitor terminal 2c is connected to the television monitor terminal 2f via the trunk line L5.

FIG. 2 is a view showing the system with a camera and each of the television monitor terminals 2a and 2b shown in FIG.
It is a block diagram which shows the circuit structure of 2c, 2d, 2e, 2f. As shown in FIG. 1, the camera-equipped entrance device 1 includes an oscillator 13 for outputting a video signal S1, a main line amplifier 10 having a signal generation source 11, and a balanced impedance (output) connected to a transmission line L0. Impedance) with an output resistance 12 of Z0 / 2.

Each of the television monitor terminals 2a, 2b, 2c, 2
d, 2e and 2f are terminating resistors 20a and 20f for receiving the input video signal S1 at the characteristic impedance Z0 of the main line.
b, 20c, 20d, 20e, and 20f, and the terminating resistor 20
a, 20b, 20c, 20d, 20e, and 20f, amplifiers 21a, 21b, and 2a that amplify the video signal S1 received by 20f.
1c, 21d, 21e, 21f and amplifiers 21a, 21
b, 21c, 21d, 21e, 21f, television monitors 22a, 22b, 22c for reproducing the video signal S1 via 21f,
22d, 22e, 22f and the above-mentioned terminating resistors 20a,
0b, 20c, 20d, 20e, and 20f, and amplifies the video signal S1 received by the signal sources 24a, 24b, and 2 again.
4c, 24d, 24e, and 24f, the main amplifiers 23a, 2d that output the video signal S1 having the output impedance Z0.
3b, 23c, 23d, 23e, and 23f, and an output impedance Z0 provided in a balanced type connected to each trunk line.
/ 2 output resistances 25a, 25b, 25c, 25d, 25
e, 25f.

The transmission line L0 is connected to the output side of the main line amplifier 10 of the camera-equipped entrance device 1 in which the oscillator 13 is connected to the input side.
, An input side of an amplifier 21a having a television monitor 22a connected to an output side, and a main amplifier 23a via a terminal resistor 20a of the television monitor terminal 2a.
Are connected respectively. Main line amplifier 23a
Are connected to the output resistors 25a respectively connected to the main lines L1 and L2, and the terminating resistors 2 of the TV monitor terminals 2b and 2c.
The input sides of the amplifiers 21b and 21c whose output sides are connected to the television monitors 22b and 22c, and the input sides of the main line amplifiers 23b and 23c are connected to the output sides via 0b and 20c, respectively. The output side of the main line amplifier 23b has output resistors 25 connected to the main lines L3 and L4, respectively.
b, terminating resistors 20d, 2d of the TV monitor terminals 2d, 2e
0e, the television monitor 22d on the output side,
An input side of amplifiers 21d and 21e to which 22e is connected;
The input sides of the main amplifiers 23d and 23e are connected respectively. Further, the trunk line L5 is connected to the output side of the trunk line amplifier 2c.
The output monitor 25f is connected to the output side via an output resistor 25c connected to the TV monitor terminal 2f and a terminal resistor 20f of the TV monitor terminal 2f.
Is connected to the input side of the amplifier 21f to which the main line amplifier 23 is connected.
The input side of f is connected.

The operation of the thus configured television intercom apparatus will be described below with reference to the block diagram of FIG. Oscillator 1 of front door unit 1 with camera
3 is output from the signal source 11 of the main amplifier 10 to the video signal S1 having the characteristic impedance Z0.
Is sent as Here, since the output resistor 12 connected to the transmission line L0 is provided in a balanced type, each impedance becomes Z0 / 2, and the output resistance 12 is connected to the terminal resistance 20a of the characteristic impedance Z0 of the television monitor terminal 2a via the transmission line L0. Received. Received video signal S1
Is amplified through the amplifier 21a, and the television monitor 22a
And is input to the main amplifier 23a.

The main amplifier 23a to which the video signal S1 has been input
Outputs the video signal S1 having the output impedance Z0 from the signal source 24a again. The video signal S1 is supplied to the terminating resistors 20b and 20c of the characteristic impedance Z0 of the television monitor terminals 2b and 2c via the main lines L1 and L2 connected to the output resistor 25a having the balanced output impedance Z0 / 2. Is received at. The received video signal S1 is amplified via the amplifiers 21b and 21c, reproduced on the television monitors 22b and 22c, and input to the main amplifiers 23b and 23c, respectively.

Signal source 23 to which video signal S1 is input
b and 23c output the video signal S1 having the output impedance Z0 from the signal sources 24b and 24c again. The video signal S1 is a main line L3 connected to output resistors 25b and 25c having a balanced output impedance of Z0 / 2.
And the TV monitor terminal 2 via L4 and L5, respectively.
Termination resistance 2 of characteristic impedance Z0 of d, 2e, 2f
0d, 20e, and 20f. The received video signal S1 is amplified via the amplifiers 21d, 21e and 21f and reproduced by the television monitors 22d, 22e and 22f, respectively, and is also reproduced by the main amplifiers 23d, 23e and 2f.
3f, respectively, and the signal generation sources 24d, 24e,
From 24f, it is output again as a video signal S1 having an output impedance Z0.

Each of the television monitor terminals 2a, 2b, 2c, 2d, terminated by the characteristic impedance Z0 of the trunk lines L1, L2, L3, L4, L5 shown in the block diagram of FIG.
2e and 2f are schematic diagrams of FIG. 3A and FIG.
Can be represented as a simplified schematic diagram of FIG. 3 (a) and 3 (b), the voltage reflection coefficient (voltage of reflected wave / voltage of incident wave) of video signal S1 at an arbitrary position on the trunk line is expressed by equation (1). Show.

[0022] Γ = (Z0-Z0 / 2 ) / (Z0 + Z0 / 2) ····· (1) also shows in (1) ² (2) power reflection coefficient is calculated gamma that from Eq. Γ ² = 1/9 (2) That is, for example, the video signal S1 output from the signal source 24a of the main amplifier 23a of the television monitor terminal 2a.
Assuming that the signal voltage of the signal generator is 1, only 1/9 of the signal generator 24
a, and the remaining 8/9 are reliably received by the terminating resistors 20b, 20c of the television monitor terminals 2b, 2c, respectively, and the multi-reflection can be reduced.

As shown in the schematic diagram of FIG. 4, when N television monitor terminals are connected, the voltage reflection coefficient (voltage of reflected wave / voltage of incident wave) of video signal S1 at an arbitrary position on the trunk line is determined. ) ΓN is shown in equation (3). ΓN = {Z0-Z0 / ( N-1)} / {Z0 + Z0 / (N-1)} ····· (3) In addition, the power reflection coefficient GanmaN ² calculated from the equation (3) (4) It is shown in the formula.

{N ² = {(N−2) / N} ² (4) Further, Table 1 shows the calculation results.

[0025]

[Table 1]

In the above embodiment, a trunk line, which is a transmission line for audio signals connecting a plurality of intercom terminals,
Although a main line, which is a transmission line of a video signal connecting a plurality of television monitor terminals, is used separately, as another embodiment of the present invention, as shown in the block diagram of FIG. By providing a duplexer (DUP: branch / distributor) for multiplexing and transmitting a video signal and using a two-wire mutual system, bidirectional communication can be performed for each terminal.

[0027]

As is apparent from the above description, according to the television intercom apparatus of the present invention, the input impedance of the video signal transmitted to a plurality of television monitor terminals is reduced.
By terminating with the terminating resistor of the characteristic impedance of the main line and amplifying with the characteristic impedance (output impedance) of the main line and outputting from the main line amplifier, it is possible to eliminate the cause of multi-reflection of the transmitted video signal. A plurality of television monitor terminals can be connected to the main line amplifier provided through the main line via the main line, and the degree of freedom of wiring can be improved without using a branching / distributing device.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing one embodiment of a television intercom apparatus according to the present invention.

FIG. 2 is a block diagram showing a circuit configuration of the camera-equipped entrance terminal and a plurality of television monitor terminals of FIG. 1;

3A is a schematic diagram of each television monitor terminal shown in FIG. 2. FIG. (B) is a schematic diagram which simplified FIG. 3 (a).

FIG. 4 is a schematic diagram when N television monitor terminals shown in FIG. 3 are installed.

FIG. 5 is a block diagram showing a circuit configuration of a system used in another embodiment of the television intercom apparatus according to the present invention.

FIG. 6 is a system configuration diagram showing a conventional television intercom apparatus.

FIG. 7 is a block diagram showing a circuit configuration of the camera-equipped entrance terminal and a plurality of television monitor terminals of FIG. 6;

FIG. 8 is a block diagram showing a circuit configuration when a plurality of television monitor terminals of FIG. 7 are connected in parallel.

[Explanation of symbols]

L1, L2, L3, L4, L5 ... trunk line 2a, 2b, 2c, 2d, 2e, 2f ... a plurality of television monitor terminals 23a, 23b, 23c, 23d, 23e, 23f ...・
.Main line amplifiers 24a, 24b, 24c, 24d, 24e, 24f ...
· Signal source S1 ···· Video signal Z0 ····· Characteristic impedance (output impedance)

Claims (2)

[Claims] A main line (L1, L1) for transmitting a video signal (S1).
2, L3, L4, L5) on multiple TV monitor terminals (2
a, 2b, 2c, 2d, 2e, 2f), the multi-reflection being reduced by terminating the plurality of television monitor terminals at the characteristic impedance (Z0) of the main line, respectively. A television intercom device for transmitting a video signal and enabling free wiring. 2. The television monitor terminal amplifies the video signal in the television monitor terminal and re-amplifies the signal to a signal source (24).
a, 24b, 24c, 24d, 24e, 24f) as the main line amplifier (2
3. The television intercom apparatus according to claim 1, further comprising: 3a, 23b, 23c, 23d, 23e, and 23f).