JP2000341422A - Television doorphone device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a television doorphone device which can detect master machine which is located at the farthest end. SOLUTION: A television doorphone device detects whether a cable 3 is connected to the terminal 52 of a master machine 2 by means of a cable connection detector 53 and closes a terminating switch 54 for connecting the cable 3 by means of terminating equipment 56, according to the detecting output of the detector 53. Opening/closing state of the switch 54 is detected by means of a termination detector 55, and the signal level in the opened/closed state of the switch 54 is detected by means of a signal level detector 57. Impedances of the cable 3 and terminating equipment 56 are automatically adjusted, so that the signal level when the switch 54 is closed becomes one half that of the signal level, when the switch 54 is opened.

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 control for matching with a characteristic impedance of a cable.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the entire structure of a conventional television door phone apparatus. In FIG. 6, the TV intercom apparatus is a door intercom slave unit (hereinafter abbreviated as a slave unit) 1 having a TV camera for imaging a visitor, and one or a serial connection having a TV monitor for displaying a captured video signal. A plurality of doorphone master units (hereinafter abbreviated as master units) 2 are connected by a cable 3, and a terminator 4 having an impedance substantially equal to the characteristic impedance of the cable is connected to the end of the cable 3.

FIG. 7 is a block diagram of the slave unit shown in FIG. 6, and FIG. 8 is a block diagram of the master unit. The slave 1 is a television camera 11, a video FM modulator 12 for modulating a video signal from the television camera 11, and a power supply from the master 2 to generate a predetermined voltage to supply power to the slave 1. It comprises a voltage regulator 13 and a transceiver 14.

A transceiver 14 is connected to a transformer 15 and a coupling capacity 1.
6 and a coil 17 for a high-frequency element.
The video modulated signal is converted from an unbalanced signal into a balanced signal, and transmitted to the base unit 2 via the cable 3.

On the other hand, as shown in FIG. 8, a master unit 2 includes a transceiver 11 and a video FM demodulator 22 for demodulating a video modulation signal.
A television monitor 23 that receives a signal from the video FM demodulator 22 and displays a video image captured by the television camera 11;
It is composed of a main unit 2 and a power supply 24 for supplying electric power to the child unit 1. The transceiver 21 is configured in the same manner as the transceiver 14 of the slave 1, and the video modulation signal transmitted from the slave 1 is returned from a balanced signal to an unbalanced signal.

[0006]

In a conventional television door phone apparatus, it is common that the terminator 4 is built in the master unit 2, and the terminal is opened and closed by opening and closing a switch attached to the terminator 4. Is performed. For this reason, the TV door phone device may be installed in an abnormal state, such as when the TV door phone device is forgotten at the time of installation or double and triple terminated.

[0007] Further, since the cable 3 is installed in various ways, for example, a single wire of two parallel wires of 0.5φ, 0.65φ, 0.9φ or a twisted wire of two parallel wires, the characteristic impedance of the cable is also various. Value.

On the other hand, since the terminator 4 uses a fixed resistor, even if the terminator 4 is properly installed, the matching with the characteristic impedance of the cable 3 is not always optimal. For this reason, the terminator 4 cannot be matched with the characteristic impedance of the cable, and the video signal captured by the television camera 11 of the slave 1 is affected by the reflection, and the performance is deteriorated. In particular, in the case of a color signal, both the amplitude and phase characteristics of the signal are affected, so that performance degradation is more noticeable than a monochrome signal.

[0009] Therefore, a main object of the present invention is to provide a television intercom apparatus that can easily determine which of the parent devices should be opened and closed.

[0010]

The invention according to claim 1 is
A door phone handset having a TV camera for imaging a visitor, a TV monitor for receiving and projecting images taken by the TV camera via a cable, and a switch capable of opening and closing a terminator having an impedance substantially equal to the characteristic impedance of the cable TV intercom apparatus in which one or more intercom master units are connected in series on a cable, and detects the farthest end master unit as seen from the intercom slave unit. It comprises a detecting means.

The invention according to claim 2 includes a terminator detecting means for detecting whether or not the terminator of claim 1 is terminated.

In the invention according to claim 3, means for automatically terminating the farthest master unit is provided.

In the invention according to claim 4, the terminator according to claim 1 is configured so that the value of its impedance can be varied.

In the invention according to claim 5, the slave unit transmits a setting signal for setting the value of the terminator.

In the invention according to claim 6, the terminator of claim 4 automatically sets the value.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment of the present invention, one slave unit 1 is connected to a plurality of master units 2 and 2 in the same manner as in FIG.
2 is connected to the base unit 2 by a cable 3, and a terminator 4 is built in the base unit 2.

FIG. 1 is a block diagram showing a terminal connection portion of a cable of a master unit according to an embodiment of the present invention. In FIG. 1, terminal unit 5 of base unit 2 includes an input terminal 51 for connecting a cable from slave unit 1 and an output terminal 52 for connecting a cable to a base unit connected in series at a subsequent stage. A cable connector 53 is connected to the output terminal 52, and the cable connector 53 detects whether or not the cable 3 is connected to the terminal 52. The detection signal is displayed on the television monitor 23 via the transceiver 21 shown in FIG. 8, and the installer opens and closes the termination switch 54 according to the signal. That is, if the cable 3 is not connected to the terminal 52, the terminal 3 becomes the farthest master from the slave 1, so that the termination switch 54 is closed.

An end detector 55 is provided to detect the open / close state of the end switch 54. The detection output of the termination detector 55 is also displayed on the television monitor 23 via the transceiver 21, so that the installer can confirm whether or not the farthest end parent device 2 has been terminated.

The terminal switch 54 of the farthest master unit may be closed upon receiving the detection signal of the cable connection detector 53.

Further, the impedance of the terminator 56 is made variable, and the installer adjusts the impedance of the terminator 56 to an optimum value while measuring the signal level of the terminal 52 of the farthest end master unit. That is, the termination switch 5
By adjusting the signal level when the signal switch 4 is closed to be half the signal level when the terminating switch 54 is open, the impedance of the cable 3 and the terminator 56 can be adjusted to an optimum value. Become.

In order to adjust the impedance of the terminator 56, an adjustment signal may be transmitted from the slave unit 1 so that the adjustment can be easily performed. In that case, a video FM signal can be used as the adjustment signal. That is, if the modulation with the video signal from the television camera 11 is stopped and the unmodulated FM carrier signal is transmitted from the slave 1,
The signal has a constant amplitude and frequency.

Further, in order to detect the signal level in the open / closed state of the termination switch 54, the signal level detector 5
7 may be provided. In this case, the signal level when the termination switch 54 is closed is
Automatically adjust the impedance of the cable 3 and the terminator 56 so that the signal level becomes １ ／ of the signal level when the signal is opened.

FIG. 2 is a diagram showing an example of the cable connection detector shown in FIG. In FIG. 2, a through hole through which the conductor 31 of the cable 3 penetrates is formed in the terminal 52,
A detection terminal 131 is provided facing the terminal 51. This detection terminal 531 also has a through hole,
The conductor 31 of the cable 3 is inserted into the through hole of the detection terminal 531 and the terminal 52, and the terminal 52 and the detection terminal 531 are short-circuited. The detection terminal 531 is connected to a positive terminal of the operational amplifier, and a reference voltage divided by a resistor is applied to a negative terminal. When the terminal 52 and the detection terminal 531 are short-circuited, the signal supplied to the terminal 52 is
When the signal level is higher than the reference voltage, the operational amplifier 533 outputs a detection signal 532 indicating that the cable 3 is connected.

FIG. 3 is a diagram showing an example of the termination detector 55 shown in FIG. In FIG. 3, the termination switch 54 is opened and closed in conjunction with another switch 60. One end of the switch 57 is grounded, and the other end is connected to a power supply voltage via a resistor. Therefore, when the termination switch 54 is closed, another switch 60 is also closed, and the detection signal 50 indicating that the termination switch 54 is closed is output.

FIG. 4 is a diagram showing a configuration in which a detection signal of the cable connection detector 53 is received, and the termination switch 54 of the farthest parent device is automatically closed.

In FIG. 4, the detection signal of the cable end detector 53 is input to a buffer 58, one end of a relay coil 59 is connected to the output of the buffer 58, and a DC power supply + B is applied to the other end of the relay coil 59. Have been. As the termination switch 54, a relay contact is used. When the cable 3 is not connected to the terminal 52, the detection signal of the cable end detector 53 is at “L” level, and when this detection signal is input to the buffer 58, the relay coil 59
, And the termination switch 54 is closed. Therefore, in this example, when the cable 3 is connected to the terminal 52, the terminal 52 of the farthest parent device can be automatically terminated.

FIG. 5 is a block diagram showing a configuration for adjusting the impedance of the terminator. In FIG.
Is connected to the input of the signal level detector 61. The signal level detector 61 is composed of a buffer and an integrator, and the output of the signal level detector 61 is an A / D converter 6
2 and the analog signal level is converted into a digital signal and supplied to the computer 63. As the computer 63, for example, a microcomputer is used. The terminating resistor 64 is composed of a plurality of resistors having different resistance values.

When the computer 63 opens all of the resistors of the terminator 64, the signal level detector 61 detects the signal level of the terminal 52, and outputs the detected signal to the A / D converter.
The converter 62 converts the digital signal into a digital signal,
Reads the value. The computer 63 sequentially short-circuits each of the terminating resistors 64, and sets the resistance value of the terminator 64 so that the signal level becomes 1/2 of the level when the above-mentioned resistors are opened. Thereby, the value of the terminator 64 can be automatically set.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0030]

As described above, according to the present invention, since the master unit at the final end can be detected, the installer can connect the cable to any of the terminals of the master unit when installing the master unit later. Can be easily known.

More preferably, if the last master unit is displayed on the monitor, the state of the terminator of the master unit can be known by looking at the monitor. It can be easily discriminated whether or not it is terminated or double-triple terminated.

In addition, by automatically terminating the farthest-end master unit, there is no need to check the state of the terminator or open / close the terminator, thereby simplifying installation work. By varying the impedance value of the terminator, various cables can be terminated at an optimum value, and signals can be transmitted without being affected by signal reflection.

Further, by transmitting the setting signal from the slave unit, the value of the terminator can be easily set. further,
By automatically setting the value of the terminator, the trouble of adjustment can be saved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a terminal connection portion of a cable of a master unit according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a cable connection detector illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of an end detector illustrated in FIG. 1;

FIG. 4 is a diagram showing a configuration in which a detection signal of a cable connection detector is received and a terminal switch of a farthest end parent device is automatically closed.

FIG. 5 is a block diagram showing a configuration for adjusting the impedance of a terminator.

FIG. 6 is a schematic block diagram of a conventional TV door phone apparatus.

FIG. 7 is a block diagram of the slave unit shown in FIG. 6;

FIG. 8 is a block diagram of the parent device shown in FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 slave unit 2 base unit 3 cable 4, 56, 64 terminator 5 connection terminal unit 11 TV camera 12 video FM modulator 13 constant voltage regulator 14, 21 transceiver 22 video FM demodulator 23 TV monitor 24 power supply 51, 52 terminal 53 Cable Connection Detector 54 Termination Switch 55 Termination Detector 57 Signal Level Detector 58 Buffer 59 Relay Coil 60 Switch 61 Signal Level Detector 62 A / D Converter 63 Computer

Claims (6)

[Claims] 1. An intercom unit having a television camera for photographing a visitor, a television monitor for receiving and projecting an image photographed by the television camera via a cable, and an impedance substantially equal to the characteristic impedance of the cable. In a TV intercom apparatus, one or more intercom master units with a switch that can open and close the terminator are connected in series on the cable, and whether or not the intercom master unit is the farthest end as viewed from the intercom slave unit. A television door phone device, comprising: a farthest end parent device detecting means for detecting. 2. The television intercom apparatus according to claim 1, further comprising a terminator detecting means for detecting whether or not the terminator is terminated in the master unit. 3. The video doorphone apparatus according to claim 1, further comprising means for automatically terminating the farthest end parent device. 4. The video doorphone apparatus according to claim 1, wherein the terminator has a variable impedance value. 5. The television doorphone device according to claim 4, wherein the slave unit transmits a setting signal for setting the variable impedance value. 6. The video door phone apparatus according to claim 4, wherein the terminator can automatically set the value of its impedance.