JP3195697B2 - Two-wire audio / video signal multiplex transmission 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 point-to-multipoint multiplex transmission of a video signal and an audio signal in a two-wire audio / video multiplex transmission system represented by a camera door phone system using a pair of wires. The present invention relates to a two-wire audio / video multiplex transmission system which can be performed in a connection mode.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing an example of a connection form of a two-wire audio / video multiplex transmission system represented by a camera door phone system.

Referring to FIG. 9, the configuration of a conventional two-wire audio / video multiplex transmission system will be described.

That is, the conventional two-wire audio / video multiplex transmission system includes a camera-equipped door phone handset 181 for multiplex transmission of an audio signal, a video signal modulated in a frequency band not overlapping the audio signal frequency band, and a DC current. 182
, An intercom with a television 196 having an audio transmission device 197 for transmitting an audio signal, and an image reception device 198 for receiving a video signal and supplying a direct current, an intercom slave unit 181 or 182 with a camera, and an optional camera intercom system. And a central control device 183 that controls the line with the door phone 196 connected to the television and enables transmission of audio signals and video signals.
83 is a pair wire h with the door phone slave unit 181 with a camera.
1, h2, and is connected to the camera-equipped door phone slave unit 182 via pair wires i1, i2.

The central control unit 183 and the doorphone with a television include a trunk line j7 comprising two pairs of information lines j1, j2 and j3, j4 and a pair of control lines j5, j6, and two pairs of information lines k1, k2. And k3, k4 and a pair of control lines k5, k6, a branch line k7, and two pairs of information lines l1, l2 and l3, l4.
And a pair of control lines l5 and l6, an audio signal transmission line l7, and a video signal transmission line n1, n2.
And a pair of m1 and m2.

[0006] The two pairs of information lines j owned by the main line j7 described above.
1, j2 and j3, j4 and a pair of control lines j5, j6;
Two pairs of information lines k1 and k2 owned by the branch line k7 are connected to k3 and k4 and a pair of control lines k5 and k6 via a main branch 184, and two pairs of information lines k1 and k2 owned by the branch line k7.
, K3, k4 and a pair of control lines k5, k6, and two pairs of information lines l1, l2 and l3, l4 owned by an audio signal dedicated transmission line l7.
And a pair of control lines l5 and l6 and a pair of video signal dedicated transmission lines n1 and n2 and a pair of m1 and m2 are connected via a dwelling unit switch 190.

Further, two pairs of information lines j1, j owned by the main line j7
2 and j3, j4, two pairs of information lines j1, j2 and j3 owned by the main line j7 in the frequency band of the video signal.
A main line terminator 187 having matching with the characteristic impedance of j4 and having a higher impedance characteristic in a lower frequency band than the video signal is provided, and at the end of two pairs of information lines k1, k2 and k3, k4 owned by the branch k7. Are two pairs of information lines k1, owned by branch k7 in the frequency band of the video signal.
A branch line terminator 193 that matches the characteristic impedances of k2, k3, and k4 and has a higher impedance characteristic in a lower frequency band than the video signal is provided.

Here, the trunk branch 184 is connected between an arbitrary point of the trunk j7 and one end of the branch k7, and converts the audio signal into two pairs of information lines j1, j2 and j3, j owned by the trunk j7.
Four pairs of information lines k1, k2, and k owned by branch line k7
3 and k4, receive DC current from two pairs of information lines j1, j2 and j3, j4 owned by the main line j7,
The video signal is transferred to two pairs of information lines j1, j2 and j owned by the main line j7.
3 and j4 with high input impedance, and two pairs of information lines k1, k2 and k3, k4 possessed by the branch line k7 in the frequency band of the video signal, and two pairs possessed by the branch line k7 having output impedances matched. Information lines k1, k2 and k
The control lines j5 and j6 owned by the main line j7 and the control lines k5 and k6 owned by the branch line k7 are directly attached.

The branching unit 190 is connected between an arbitrary portion of the branch line k7, an end of the audio signal transmission line 17 and an end of the video signal transmission lines m1, m2 and n1, n2. Receive direct current from the video signal dedicated transmission lines m1, m2 and n1, n2, and provide information lines k1, k owned by branch line k7.
2, k3, and k4, and the information lines l1, l2, l3, and l4 owned by the audio signal dedicated transmission line l7, and the video signal is bidirectionally transmitted, and the video signal is transmitted through the information lines k1, k2 and k3, k4 owned by the branch line k7. And balanced reception with a high input impedance from the video signal transmission lines m1, m2 and n in the frequency band of the video signal.
1 and n2, and branch lines 191 and 192 for unbalanced transmission to video signal dedicated transmission lines m1 and m2 and n1 and n2 with output impedance matched to control lines k5 and k6 owned by branch line k7 and sound. Control line l owned by signal transmission line l7
5 and l6 are directly attached.

Conventionally, a transformer using a transformer is used as the dwelling unit 190 of the two-wire audio / video multiplex transmission system configured as described above.

FIG. 10 is a circuit diagram showing a configuration of a branch line branching portion provided in a conventional dwelling unit branch unit. The configuration will be described with reference to FIG.

The branch line branching section 199 is composed of an unbalanced transmission section 201 for transmitting a video signal and converting balance to unbalanced, and a low-band signal separation section 200 for transmitting an audio signal. 209 is an information line k1, k owned by the branch line
2 (or k3, k4) and terminals 210, 21
1 is connected to the information lines 11 and 12 (or 13 and 14) owned by the audio signal transmission line, and the terminals 212 and 213 are connected to the video signal transmission lines n1 and n2 (or m1 and m2).

Next, the operation will be described with reference to FIG.

That is, in the unbalanced transmission unit 201, the video signal input to the terminals 208 and 209 in a balanced state is output to the capacitors 204 and 205 and the high input impedance.
In the frequency band of the video signal, the transmission line dedicated to the video signal m
The signal passes through a transformer 206 which has an output impedance characteristic matched with the characteristic impedance of 1, m2 or n1, n2 and is output unbalanced via a capacitor 207, and is output from terminals 212 and 213. At this time,
The audio signal is blocked by the capacitors 204 and 205.

On the other hand, in the low-band signal separating section 200, the audio signal is transmitted to the coils 202a and 202b and the capacitor 20a.
3a, 203b and terminals 208, 209
Bidirectional transmission between the terminal and the terminals 210 and 211 is enabled. At this time, the coils 202 and 203 block the passage of the video signal.

[0016]

However, in the above-described configuration of a dwelling unit switch using a conventional transformer,
Despite the need for a transformer having a uniform high input impedance characteristic in the frequency band of the video signal,
It was technically difficult to produce the required transformer. For this reason, a transformer having a non-uniform high input impedance characteristic in the frequency band of the video signal has to be used, which is a factor of causing the transmission degradation of the video signal.

Further, since the number of turns of the input side coil of the transformer is considerably larger than the number of turns of the output side coil, there is a drawback that the transmission signal level is lowered when the video signal passes.

Further, since the cost of the transformer increases,
There is also a problem that the cost of the entire system is increased.

Furthermore, since there is a limit to downsizing of the transformer, there is a disadvantage that it is difficult to reduce the size and weight of the main body.

In addition, there is no function of selecting and transmitting a received video signal, and two pairs of video signal dedicated transmission lines are required (that is, the same number of pairs of camera-equipped intercom units with cameras). There was also. .

That is, there is a problem as described above in a dwelling unit switch using a conventional transformer.

On the other hand, the use of a pair line for the main line and the branch line causes a problem that the attenuation of the video signal is large and the wiring scale of the system is restricted, making long-distance transmission difficult.

[0023]

An object of the present invention is to provide a repeater that amplifies a video signal, which has been attenuated by long-distance transmission, to a predetermined transmission signal level in consideration of such a problem of a conventional branching device. .

[0025]

According to the present invention, there are provided a plurality of slave units with a camera, a trunk line or a branch line connected to the slave units with a camera, and a dwelling unit connected to the trunk line or the branch line. In a two-wire audio-video signal multiplex transmission system including a branch unit and a master unit with a television connected to the unit branch unit, a repeater provided with an amplification function provided on a main line or a branch line is provided with unbalanced conversion reception. Section and auto gain
This is a two-wire audio / video signal multiplex transmission system having a control unit and a balanced transmission unit.

According to a second aspect of the present invention, there is provided a system for multiplex transmission of an audio signal, a video signal modulated in a frequency band not overlapping with an audio signal frequency, and a DC current using a pair line, A relay connected to any of the relay points of the above , wherein the video signal is received balanced and unbalanced signal
An unbalanced conversion receiver for converting and outputting, and a predetermined transmission signal
Auto gain control to obtain a video signal adjusted to the level
Troll section, the video signal obtained in the auto gain control section, is converted to a balanced signal, maintaining the output impedance equal to the characteristic impedance of the pair wire in the frequency band of the video signal, the audio signal of It has a means for maintaining a high output impedance in a frequency band and a direct current, and is constituted by a balanced transmitting section for transmitting to the pair wire and a coil, for preventing a video signal from passing, and for transmitting a voice signal and a direct current bidirectionally. A low-pass filter unit, having means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a DC current from the pair wire, generating a specific voltage level, The unbalanced conversion receiving unit, the auto gain control unit, and a power receiving unit that supplies power to the balanced transmitting unit are provided. The unbalanced conversion receiver, the movies
Pass the image signal and pass the DC current and the audio signal
Block, equal to the pair line in the video signal frequency band
Balanced receiver that maintains characteristic impedance or high impedance
Communication means, and converts the unbalanced received video signal into
And an unbalanced transmitting means ,
The control unit controls the level of the input AC signal
Multiplied by the AC signal level reduced from the AC signal level of
To obtain a bias voltage with a predetermined voltage level increased
Half-wave rectification means, and vias obtained by the half-wave rectification means
Voltage level is higher than the specified bias voltage.
Multiplied by a minute to increase the predetermined voltage level
Amplifying means for obtaining a DC voltage for use, and the differential amplifying means
The DC voltage for adjusting the amplification obtained by
Increasing to amplify the force has been ac signal to a predetermined outgoing signal level
A repeater comprising a width adjusting unit .
The present invention according to claim 3 is used for a system that multiplexes a video signal and a DC current modulated in a frequency band that does not overlap with an audio signal frequency by using a pair wire, and an arbitrary one of the pair wire. A relay connected to a relay point, wherein the video signal is balanced and converted to an unbalanced signal and output.
Input unbalanced conversion receiver, and adjust to a predetermined transmission signal level.
Auto gain control section to obtain a reduced video signal
And converting the video signal obtained by the auto gain control section into a balanced signal, maintaining an output impedance equal to the characteristic impedance of the pair wire in the frequency band of the video signal, And a means for maintaining a high output impedance in direct current, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of video signals and for transmitting audio signals and direct current bidirectionally. A pass filter unit, and means for maintaining a high input impedance in a frequency band of the video signal and a frequency band of the audio signal, receiving a DC current from the pair wire, generating a specific voltage level, and a power receiving unit that supplies power to said balanced transmission section and the balanced converter receiving unit and the automatic gain control unit, the non衡conversion receiver, said video signal
Passing, blocking the direct current and the audio signal,
In the video signal frequency band, the characteristic impedance equal to the pair line is used.
Balanced receiving means to maintain impedance or high impedance
And unbalanced conversion of the balanced received video signal and output
Unbalanced transmission means, and the balanced reception means
Passing the image signal and blocking the DC current and the audio signal.
The capacitor to stop and the video signal frequency band
Characteristic impedance or high impedance
Connected via a bias member to maintain the characteristics and performance
Equal first active electronic component and second active electronic component
The auto gain control section has an input
The input AC signal level is higher than the specified AC signal level.
Multiply the reduced AC signal level by a predetermined voltage level
Half-wave rectification means for obtaining a bias voltage with increased
The bias voltage obtained by the half-wave rectifier is
Multiplied by the voltage level increased from the ground voltage,
Difference to obtain DC voltage for amplification adjustment with increased voltage level
Dynamic amplification means, and the amplification degree adjustment obtained by the differential amplification means.
A predetermined DC voltage is used to adjust the input AC signal.
And amplifying adjustment means for amplifying the signal to the transmission signal level . The present invention according to claim 4 is used in a system for multiplexing a video signal and a DC current modulated in a frequency band that does not overlap with an audio signal and an audio signal frequency using a pair line, and using any pair line. A repeater connected to a relay point, wherein the video signal is balanced and received.
Unbalanced conversion receiving unit
When, Oh obtaining a video signal adjusted to a predetermined outgoing signal level
And a video signal obtained by the auto gain control section and converted into a balanced signal to maintain an output impedance equal to the characteristic impedance of the pair wire in the frequency band of the video signal. A means for maintaining a high output impedance in the frequency band and direct current of the audio signal, comprising a balanced transmitting section for transmitting to the pair wire, and a coil for preventing the passage of a video signal, A low-pass filter section for bi-directional transmission, and a means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a direct current from the pair wire, a specific voltage Level, and supplied to the unbalanced conversion receiving unit, the auto gain control unit, and the balanced transmitting unit. And a power receiving unit that, the unbalanced strange
The exchange receiving unit passes the video signal, and outputs the DC current and
Blocking the audio signal, in the video signal frequency band
Characteristic impedance or high impedance equal to the pair wire
Balanced receiving means for maintaining the dance,
And unbalanced transmission means for unbalanced conversion and output of the signal.
The unbalanced transmitting means may be a first active electronic component or a second active electronic component.
The video signal output from the active electronic component is
Unbalanced output with impedance receiving means for receiving and outputting
It has an active electronic component for force, the automatic gain co
The controller controls the input AC signal level to
Multiply the AC signal level that is lower than the AC signal level
To obtain a bias voltage with a predetermined voltage level increased
Half-wave rectification means, and vias obtained by the half-wave rectification means
Voltage level is higher than the specified bias voltage.
Multiplied by a minute to increase the predetermined voltage level
Amplifying means for obtaining a DC voltage for use, and the differential amplifying means
The DC voltage for adjusting the amplification obtained by
Amplifying the input AC signal to a predetermined transmission signal level.
A repeater comprising a width adjusting unit .
The present invention according to claim 5 is used for a system that multiplexes a video signal and a DC current modulated in a frequency band that does not overlap with an audio signal frequency by using a pair line, and an arbitrary one of the pair line. A relay connected to a relay point, wherein the video signal is balanced and converted to an unbalanced signal and output.
Input unbalanced conversion receiver, and adjust to a predetermined transmission signal level.
Auto gain control section to obtain a reduced video signal
And converting the video signal obtained by the auto gain control section into a balanced signal, maintaining an output impedance equal to the characteristic impedance of the pair wire in the frequency band of the video signal, And a means for maintaining a high output impedance in direct current, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of video signals and for transmitting audio signals and direct current bidirectionally. A pass filter unit, and means for maintaining a high input impedance in a frequency band of the video signal and a frequency band of the audio signal, receiving a DC current from the pair wire, generating a specific voltage level, and a power receiving unit that supplies power to said balanced transmission section and the balanced converter receiving unit and the automatic gain control unit, the non衡conversion receiver, said video signal
Passing, blocking the direct current and the audio signal,
In the video signal frequency band, the characteristic impedance equal to the pair line is used.
Balanced receiving means to maintain impedance or high impedance
And unbalanced conversion of the balanced received video signal and output
Unbalanced transmission means, and the balanced reception means
Passing the image signal and blocking the DC current and the audio signal.
The capacitor to stop and the video signal frequency band
Characteristic impedance or high impedance
Connected via a bias member to maintain the characteristics and performance
Equal first active electronic component and second active electronic component
Wherein the unbalanced transmitting means comprises a first active electronic unit.
The video signal output from the product or the second active electronic component
Signal with high input impedance receiving means and output
It has an active electronic component for unbalanced output of said auto
・ The gain control section
Signal level is lower than the specified AC signal level.
Bias multiplied by the specified voltage level
A half-wave rectifier for obtaining a voltage,
The obtained bias voltage has increased from a predetermined bias voltage.
Multiplied by the voltage level to increase the specified voltage level
A differential amplifying means for obtaining a DC voltage for adjusting the amplification degree;
The DC voltage for adjusting the amplification obtained by the dynamic amplification means
The input AC signal to a predetermined transmission signal level.
A repeater comprising amplification adjustment means for amplifying .

[0027]

[0028]

[0029]

According to the present invention, an unbalanced conversion receiving section performs balanced reception of a video signal transmitted from a pair line and converts the video signal into an unbalanced signal.
The auto gain control unit adjusts the unbalanced converted video signal to a predetermined transmission signal level, and the balanced transmission unit balances and transmits the video signal adjusted to the predetermined transmission signal level to a pair line, The low pass filter section
The video signal is blocked and the audio signal and the DC current are transmitted bidirectionally.

[0030]

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of a connection form of a two-wire audio-video multiplex transmission system represented by a camera door phone system according to an embodiment of the present invention, and the configuration will be described.

In FIG. 1, a two-wire audio / video multiplex transmission system includes a camera-equipped door phone handset 1 for multiplex transmission of an audio signal, a video signal modulated in a frequency band not overlapping the audio signal frequency band, and a DC current. And 2, an intercom with a television 17 having an audio transmission device 18 for transmitting an audio signal, and an image receiving device 19 for receiving a video signal and supplying a direct current, and an intercom slave unit 1 or 2 with a camera.
And a central control device 3 that controls the line with a TV intercom 17 connected to an arbitrary part of the camera intercom system to enable transmission of audio signals and video signals. The camera doorphone slave device 1 is connected to the camera doorphone slave device 2 via pair wires a1 and a2, and the camera doorphone slave device 2 is connected to the camera doorphone slave device 2 via pair wires b1 and b2.

The central control unit 3 and the intercom with a television have a trunk c7 comprising two pairs of information lines c1, c2 and c3, c4 and a pair of control lines c5, c6, and two pairs of information lines d1, d2, d3, d4 and a pair of control lines d5, d6
And a pair of information lines e1, e2 and e
3, e4 and a pair of control lines e5, e6, a branch line e7, two pairs of information lines f1, f2, f3, f4, and 1
A transmission line f exclusively for audio signals comprising a pair of control lines f5 and f6.
7 and a pair of g1 and g2, which are video signal exclusive transmission lines.

Two pairs of information lines c1, c2 and c3, c4 owned by trunk c7 and a pair of control lines c5, c6, and two pairs of information lines d1, d2, d3, d4 and one pair owned by trunk d7. The control lines d5 and d6 are connected via the repeater 4, and two pairs of information lines d1, d2 and d3, d4 and 1 owned by the trunk line d7.
A pair of control lines d5 and d6, two pairs of information lines e1, e2 and e3 and e4 owned by the branch line e7, and a pair of control lines e5 and e6.
Are connected via the main branch 7.

Also, two pairs of information lines e1, e owned by the branch line e7
2 and e3, e4 and a pair of control lines e5 and e6, two pairs of information lines e1, e2 and e3, e owned by the branch line e7.
4 and two pairs of information lines f owned by the voice signal transmission line f7
1, f2 and f3, f4 and 1 which is a video signal dedicated transmission line
The pair g1 and g2 are connected via the dwelling unit switch 13, and the control lines e5 and e6 owned by the branch line e7 and the control lines f5 and f6 owned by the audio signal dedicated transmission line f7 are directly attached.

On the other hand, two pairs of information lines d1, owned by trunk line d7
At the end portions of d2, d3, and d4, two pairs of information lines d1, d2, and d owned by trunk d7 in the frequency band of the video signal.
3, a main line terminator 10 having high impedance characteristics in a lower frequency band than the video signal is provided, and two pairs of information lines e1, e2 and e3, e4 owned by the branch line e7 are terminated. The part includes two pairs of information lines e owned by the branch line e7 in the frequency band of the video signal.
There is provided a branch line terminator 14 that matches the characteristic impedances of e1, e2, e3, and e4 and has higher impedance characteristics in a lower frequency band than the video signal.

Next, the operation of the camera intercom system will be described based on the above configuration.

Here, the repeater 4 comprises a trunk c7 and a trunk d7.
Is installed at an arbitrary relay point, and transmits the audio signal and the DC current to two pairs of information lines c1, c2 and c3, c4 owned by the main line c7.
Two pairs of information lines d1, d2 and d owned by the side and trunk d7
3 and d4 side, and receive DC current from two pairs of information lines c1, c2 and c3 and c4 owned by the main line c7,
Two pairs of information lines c1, c2, c3, and c4 owned by trunk c7 from two pairs of information lines c1, c2, and c3, c4 owned by trunk c7.
The video signal is balanced-received with an input impedance matched with the characteristic impedance of the video signal and amplified to a predetermined transmission signal level.
Two pairs of information lines d1, owned by trunk line d7 with output impedances matched between paired information lines d1, d2 and d3, d4.
It has a relay section for balanced transmission to d2, d3 and d4,
7 own control lines c5 and c6 and main line d7 own control line d
5 and d6.

The trunk branch unit 7 is connected between an arbitrary portion of the trunk line d7 and one end of the branch line e7, and outputs audio signals to two pairs of information lines d1, d2 and d3, d4 owned by the trunk line d7. And two pairs of information lines e1, e2 and e3, e4 owned by branch line e7.
Bidirectional transmission between the two sides, two pairs of information lines d owned by trunk line d7
1, d2, d3, and d4 to receive a DC current, and convert the video signal into two pairs of information lines d1, d2, d3, and d4 owned by the main line d7.
, And two pairs of information lines e1 and e owned by the branch line e7 in the frequency band of the video signal.
Control lines owned by the trunk line d7 and having two pairs of information lines e1, e2, e3, and e4 owned by the branch line e7 with balanced output impedances of the branch lines e3 and e4. d5 and d6 are directly attached to the control lines e5 and e6 owned by the branch line e7.

The branching unit 13 is connected between an arbitrary portion of the branch line k7, an end of the audio signal transmission line f7, and an end of the video signal transmission lines g1 and g2. DC current is received from the transmission lines g1 and g2, and the branch line e
7 information lines e1, e2, e3, and e4, and the audio signal dedicated transmission line f7 owned information lines f1, f2, f3, and f4.
, The video signal is balanced and received with high input impedance from the information lines e1, e2, e3, and e4 owned by the branch line e7, and two pairs of information lines f1 and f2 owned by the audio signal dedicated transmission line f7. Alternatively, a DC short-circuit state is detected from f3 and f4, and the corresponding video signal from the information line owned by the branch line e7 is output impedance matched with the video signal dedicated transmission lines g1 and g2 in the frequency band of the video signal. The transmission is unbalanced to the video signal transmission lines g1 and g2.
The control lines e5 and e6 owned by the branch line e7 and the control lines f5 and f6 owned by the audio signal dedicated transmission line f7 are directly attached.

Next, an embodiment of the repeater according to the present invention will be described with reference to the drawings (FIGS. 1 to 4).

FIG. 2 is a circuit diagram of the relay unit 5 or the relay unit 6 provided in the repeater of this embodiment, which is another example of the camera intercom system described in the above embodiment.

The configuration will be described below with reference to FIGS. 1 and 2.

That is, the connection form of the two-wire audio / video multiplex transmission system is such that two pairs of information lines c1, c owned by the trunk c7
2 and c3 and c4 each have 26 and 27, and two pairs of information lines d1, d2 and d3 and d4 owned by trunk d7 have 2
8, 29 are connected.

In FIG. 2, the relay unit 20 includes two pairs of information lines c owned by the main line c7 in the frequency band of the video signal.
1, c2 and c3, c4, are matched with the characteristic impedance, hold high input impedance in the frequency band of the audio signal and DC current, block the audio signal and DC current, and perform balanced reception and unbalanced conversion of the video signal. The unbalanced conversion receiving unit 22 to be transmitted, the auto gain control unit 23 that amplifies the video signal obtained by the unbalanced conversion receiving unit 22 and obtains a predetermined transmission signal level, and the auto gain control unit 23 Unbalanced conversion of the obtained video signal,
In the frequency band of the video signal, the characteristic impedance of the two pairs of information lines d1, d2 and d3, d4 owned by the main line d7 is matched, and the video signal is maintained while maintaining a high output impedance in the frequency band of the audio signal and the direct current. A balanced transmitting section 24 for sending, a low-pass filter section 25a composed of coils 25b and 25c having a high impedance in the frequency band of the video signal and a low impedance in the frequency band of the audio signal, and a frequency band of the video signal and the audio signal. Receives a DC current with a high input impedance, converts it to a predetermined voltage level,
2, an auto gain control unit 23, and a power receiving unit 21 that supplies power to the balanced transmitting unit 24.

The above-described unbalanced conversion receiving section 22 is similar to the unbalanced conversion receiving section 30 shown in FIG. 3, and the terminals 26 and 27 shown in FIG. 2 are connected to the terminals 47 and 48 shown in FIG. Correspondingly, the terminal 49 is connected to the auto gain control section 23 shown in FIG.

FIG. 3 is a circuit diagram showing the circuit configuration of the unbalanced conversion receiving section 30, and the configuration and operation will be described with reference to FIG.

That is, the unbalanced conversion receiving section 30 is composed of a balanced receiving section 31 and an unbalanced transmitting section 32. The balanced receiving section 31 includes the high impedance capacitors 33 and 34 and the video signal frequency in the audio signal frequency band. In the band, two pairs of information lines c1, c2 and c3 owned by the main line c7
Bias resistors 35, 36, 37 and 38 matched with the characteristic impedance of c4 are connected to the respective bases,
It comprises transistors 40 and 43 to which emitter resistors 41 and 44 and collector resistors 39 and 42 are respectively connected, and receives video signals from terminals 47 and 48 in a balanced manner.

The unbalanced transmitting section 32 is provided with a balanced receiving section 31.
And a FET 45 connected to the collector and gate of the transistor 43 and connected to the source resistor 46. The video signal received balanced by the balanced receiving section 31 is unbalanced and transmitted to the terminal 49.

The unbalanced conversion receiving section 2 of the present embodiment as described above
With the configuration of 2 (30), the bias resistors 35, 36 and 37, 38 provided in the balanced receiving section maintain uniform input impedance in the frequency band of the video signal, and the transformer takes measures when receiving the video signal. This makes it possible to avoid degradation of transmission quality typified by phase distortion, which has been difficult.

Further, in the frequency band of the audio signal, the AC impedance between the terminals 47 and 48 can be kept high by the capacitors 33 and 34, and the deterioration of the transmission quality of the audio signal due to the decrease of the AC impedance can be avoided. it can.

On the other hand, the above-mentioned auto gain control section 23 is the same as the auto gain control section 50 shown in FIG. 4, and as shown in FIG. The terminal 74 is connected to the balanced transmission unit 24 and includes a half-wave rectification unit 51, a differential amplification unit 52, and an amplification adjustment unit 53.

FIG. 4 is a circuit diagram showing the circuit configuration of the auto gain control section 50. The configuration and operation will be described with reference to FIG.

That is, the half-wave rectifying section 51 includes a transistor 55 having a terminal 73 connected to the base, a capacitor 57 connected in parallel with the emitter resistor 56, and a collector resistor 54, and a collector and a cathode of the transistor 55 connected to the transistor 55. The video signal input from the terminal 73 is half-wave rectified and smoothed by the half-wave rectification unit 51, and the video signal is smoothed. A large DC voltage is obtained for the attenuated signal level.

The differential amplifying section 52 includes a transistor 62 having an anode and a base connected to the anode of the diode 58 of the half-wave rectifying section 51 and having an emitter resistance 61, and a transistor 6
And a transistor 66 having a collector and a base connected to the collector and base of the transistor 62 and having an emitter resistor 65 and a collector resistor 67. The half-wave rectifier 5
1 obtains a DC voltage differentially amplified by the differential amplifying section 52, increases the current flowing through the pull-up resistor 63 by the increase in the DC voltage input to the transistor 62, and increases the collector resistance 67 To increase the DC voltage.

The amplification adjustment unit 53 is connected to the gate 1 via a terminal 73, a capacitor 70 and bias resistors 71 and 72, and is connected to a transistor 66 of the differential amplification unit 52.
And the gate 2 are connected to each other, a drain resistor 69 is provided, and the four-terminal FET 6 is connected to the drain and the terminal 74.
The video signal input to the gate 1 of the four-terminal FET 68 from the terminal 73 amplifies the DC voltage level obtained by the differential amplifier 52 input to the gate 2 and outputs the amplified signal from the terminal 74. .

As described above, the auto gain
The pull-up resistor 60
A capacitor 59 and a diode 58 connected in parallel with
This facilitates half-wave rectification and smoothing.

Further, by using the pull-up resistor 63 in the operating circuit, having the transistor 66, adjusting the ratio of the values of the emitter resistance and the collector resistance, and adjusting the voltage input to the gate 2 of the four-terminal FET, It is easy to set the amplification degree and adjust the offset voltage.

Here, a plurality of repeaters 4 are connected to a pair line owned by the main line for transmitting the audio signal, the video signal and the DC current, and are connected to a plurality of repeaters at arbitrary locations.

Next, an embodiment of the branching device according to the present invention will be described with reference to the drawings (FIG. 1 and FIGS. 5 to 8).

FIG. 5 is a circuit diagram of a turnout switch of this embodiment, which is another example of the camera intercom system described in the above embodiment.

Hereinafter, the configuration will be described with reference to FIGS. 1 and 5.

That is, the dwelling unit branching device 75 shown in FIG.
It is equivalent to the dwelling unit switch 13 of FIG.
96 and 97, 98 are two pairs of information lines e owned by branch line e7
1, e2 and e3, e4, and terminals 99,
100, 101 and 102 are respectively connected to two pairs of information lines f1, f2 and f3 and f4 of the audio signal transmission line f7, and the terminals 103a and 103b are connected to the video signal transmission line g.
1 and g2. Note that g1 and g2 of the video signal dedicated transmission lines are coaxial lines.

The dwelling unit splitter 75 includes an unbalanced conversion receiving unit 77 for receiving a video signal with high input impedance and performing unbalanced conversion, and capacitors 82, 83 and 84, 85 and coils 86, 87 and 88, 89. The band-pass filter section 76, which is connected in series and is connected via terminals 95, 96 and 97, 98 and the terminals 99, 100 and 101, 102, passes the audio signal, and is received by the unbalanced conversion receiving section. A video signal transmitting unit 79 for transmitting one of the two types of video signals, and a DC short-circuit state of the terminals 99 and 100 is monitored. When the terminals are open, the video signals received by the terminals 97 and 98 are transmitted. A loop detector 78 for controlling the video signal transmitted from the terminal 79 and the terminals 95 and 96 to be transmitted from the video signal transmitter 79 in a short-circuit state; Video signal dedicated transmission line g of FIG. 1 in the frequency band of the transmitted video signal from the No. transmitting section 79
1, a resistor 91 having an output impedance matched with the characteristic impedance of g2, a matching unit 80 including a pull-down resistor 90 and a capacitor 92, and a coil 9
3 and a capacitor 94, and a power receiving unit 81 that supplies a DC voltage received from the video signal dedicated transmission lines g1 and g2 to an unbalanced conversion receiving unit 77, a loop detecting unit 78, and a video signal transmitting unit 79. It consists of.

The above-described unbalanced conversion receiving unit 77 is equivalent to the unbalanced conversion receiving unit 104 shown in FIG. 6, and as shown in FIG.
5 are connected to terminals 95, 96 and 97, 98, respectively.

FIG. 6 shows an unbalanced conversion receiving unit 104.
FIG. 3 is a circuit diagram showing the circuit configuration of FIG.
The configuration and operation will be described.

That is, capacitors 105, 106 and 119, 120 having low impedance in the frequency band of the video signal and high impedance in the frequency band of the audio signal, and bias resistors 107, 108, 10 having a high impedance in the frequency band of the audio signal.
9, 110 and 121, 122 and 123, 124 are connected to the terminals 133, 134 and 135, 136 and the respective bases.
Transistor 112 with one and emitter resistor 116
A transistor 115 having an emitter resistor 127 and a collector resistor 125; a transistor 129 having an emitter resistor 130 and a collector resistor 128; and a source resistor 118 having a collector and a gate connected to the transistor 115. FET 1 with source connected to terminal 137
17 and a FET 131 having a source and a gate connected to the collector and the gate of the transistor 129 and having a source resistance 132 connected to the source and the terminal 138.
4 and 135 and 136, respectively, to unbalancedly convert the video signals received at terminals 137 and 138.

The unbalanced conversion receiving section 7 of this embodiment as described above.
7 (104), the bias resistors 107, 108 and 109, 110 and 121, 122 and 123, 124 provided in the unbalanced receiving unit 104 maintain a uniform high input impedance in the frequency band of the video signal. At the time of receiving a video signal, it is possible to avoid deterioration of transmission quality typified by phase distortion, which is difficult to take measures with a transformer.

Further, in the frequency band of the audio signal, the AC impedance between the terminals 133 and 134 is changed by the capacitors 105 and 106 to the capacitors 119 and 120.
Thus, the AC impedance between the terminals 135 and 136 can be kept high, and the deterioration of the transmission quality of the audio signal due to the decrease in the AC impedance can be avoided.

On the other hand, the above-described loop detecting section 78 is equivalent to the loop detecting section 139 shown in FIG. 7, and the terminals 158 and 159 shown in FIG. 7 are respectively connected to the terminals 99 and 100 shown in FIG. .

FIG. 7 is a circuit diagram showing a circuit configuration of the loop detecting section 139. The configuration and operation will be described with reference to FIG.

That is, the loop detecting section 139 includes a transistor 15 having an emitter resistor 150, the base of which is connected to the terminal 158 via a base resistor 156 and a capacitor 155a connected in parallel with the pull-up resistor 154a.
1, a transistor 152 having an emitter resistor 153 with a base connected to the terminal 159 via a capacitor 155b connected in parallel with a base resistor 157 and a pull-down resistor 154b, an anode connected to the collector of the transistor 151, and a pull-up resistor The terminal 1 is connected via a capacitor 145 connected in parallel with the capacitor 144 and a capacitor 141a connected in parallel with the collector resistor 140a.
42, a photocoupler 148 connected to the collector,
The cathode and the collector of the transistor 152 are connected,
The anode and the cathode of the photocoupler 148 are connected, the capacitor 147 connected in parallel with the pull-down resistor 146, and the photocoupler 149 connected to the terminal 143 and the collector via the capacitor 141b connected in parallel with the collector resistor 140b. When the terminals 158 and 159 are opened DC, the collector of the photocoupler 148 is opened to the ground,
When the emitter of the photocoupler 149 is short-circuited to the ground, and when the terminals 158 and 159 are short-circuited in terms of DC, the collector of the photocoupler 148 is short-circuited to the ground, and the emitter of the photocoupler 149 is at the power supply voltage level. .

As described above, the loop detector 78 of this embodiment is used.
With the configuration of (139), the base resistors 156 and 157 can maintain a high impedance between the terminals 99 and 100 in the frequency band of the audio signal and the video signal.

The capacitors 155a and 155b short-circuit the audio signal and the video signal in the frequency band.
The influence of the audio signal and the video signal on the control signal transmitted from the terminals 142 and 143 can be avoided.

On the other hand, the video signal transmitting section 79 described above
Is equivalent to the video signal transmission unit 160 shown in FIG. FIG.
The terminals 181 and 182 shown in FIG.
43, the terminals 179 and 180 shown in FIG. 8 are connected to the terminals 137 and 138 shown in FIG. 6, and the terminal 183 shown in FIG. 8 is connected to the terminal 103a via the matching section shown in FIG.

FIG. 8 is a circuit diagram showing a circuit configuration of the video signal transmitting section 160. The configuration and operation will be described with reference to FIG.

That is, the video signal transmitting section 160 has a base connected to the terminal 179 via the capacitor 161 and the bias resistors 163 and 164, has a collector resistor 167 and an emitter resistor 169, and has an amplifying capacitor 173.
A transistor 168 having an emitter and an amplification resistor 174 connected to the emitter, a capacitor 162 and a bias resistor 16
5, a transistor 171 having a collector connected to a terminal 180, a collector resistor 170 and an emitter resistor 172, an amplifier capacitor 175 and an amplifier resistor 176 connected to an emitter, and a base connected to a terminal 181. The switching transistor 177 has an emitter connected to the collector of the transistor 168, the collector connected to the terminal 183, the base connected to the terminal 182, the emitter connected to the collector of the transistor 171 and the collector connected to the terminal 183. When the outflow current flows from the terminal 181, the video signal input to the terminal 179 is changed to the terminal 1.
The video signal input to the terminal 180 is output to the terminal 183 when the current is output to the terminal 83 and the outflow current flows from the terminal 182.

The video signal transmitting section 16 of this embodiment as described above
0 (79), the switching transistor 17
7, 178, the two kinds of video signals can be output to the terminal 183 without being mixed by controlling the voltages of the terminals 181 and 182.

As described above, by using the repeater and the branching unit in the above embodiment in a two-wire audio / video multiplex transmission system represented by a camera door phone system, a uniform high-frequency signal in the frequency band of the video signal can be obtained. The input impedance characteristics can be secured, the transmission signal level can be prevented from lowering when the video signal passes, the cost of the entire system can be reduced, and the size and weight of the main unit can be reduced. It is possible to select and transmit the received video signal,
Further, a two-wire audio / video multiplex transmission system capable of amplifying a video signal attenuated by long-distance transmission to a predetermined transmission signal level can be realized.

Although the repeater of the present invention has been described in the above embodiment as a repeater in a two-wire audio / video multiplex transmission system typified by a camera door phone system, the present invention is not limited to this. It may be used as a branching device.

When the repeater of the present invention is used, for example, as a trunk branch unit, it does not matter whether or not it has an auto gain control unit for adjusting an input signal input to a predetermined output signal level.

In the above embodiment, the description has been given of the case of a two-wire audio / video multiplex transmission system typified by a camera door phone system. However, the present invention is not limited to this. In short, any system may be used as long as it is a two-wire transmission system, such as a system for communicating with a destination.

Although the above embodiment has been described with reference to a two-wire audio / video multiplex transmission system typified by a camera door phone system, the present invention is not limited to this. The transmission signal may be any type of signal. , One type of signal.

In the above embodiment, the photocoupler is used as the circuit configuration of the loop detecting section. However, the present invention is not limited to this, and any element may be used as long as it is an optical semiconductor element.

Further, in the above embodiment, the case where a transistor, an FET, or the like is used for the circuit configuration has been described. However, the present invention is not limited to this. What is necessary is that the circuit is configured using active electronic components. May be something.

As described above, the present embodiment has the advantages that a uniform high input impedance characteristic can be secured in the frequency band of the input signal, and that the transmission signal level can be prevented from lowering when the input signal passes. Have.

In the present embodiment, a plurality of received input signals
It has the advantage that it is possible to select and transmit the issue
You.

Further , in this embodiment, the cost of the entire system is
Can be reduced.
The advantage is that the body can be made smaller and lighter.
You.

[0090]

As apparent from the above description, the book
The invention provides a method for transmitting an attenuated input signal during transmission to a predetermined
Adjust the transmission signal level such as amplification to the signal level
It has the advantage of being able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a system for multiplexing transmission of an audio signal, a video signal, and a DC current in a two-wire audio / video multiplex transmission system according to the present invention.

FIG. 2 is a circuit diagram of a relay unit provided in the relay device of one embodiment according to the present invention.

FIG. 3 is a circuit diagram of an unbalanced conversion receiving unit included in the relay unit of FIG. 2 according to the present invention.

FIG. 4 is a circuit diagram of an auto gain control unit provided in the relay unit of FIG. 2 according to the present invention.

FIG. 5 is a circuit diagram of a turnout switch according to another embodiment of the present invention.

FIG. 6 is a circuit diagram of an unbalanced conversion receiver provided in the dwelling unit branch unit of FIG. 5 according to the present invention.

FIG. 7 is a circuit diagram of a loop detector provided in the branching unit of FIG. 5 according to the present invention.

8 is a circuit diagram of a video signal transmission unit provided in the dwelling unit branch unit of FIG. 5 according to the present invention.

FIG. 9 is a configuration diagram illustrating an example of a conventional system that multiplexes and transmits an audio signal, a video signal, and a DC current.

FIG. 10 is a circuit diagram of a branch line branching section provided in a conventional dwelling unit branching device.

[Explanation of symbols]

1, Doorphone slave unit with camera (slave unit with camera) 3 Central control unit c7, d7 Main line c1, c2, c3, c4, d1, d2, d3, d4 Information line c5, c6, d5, d6 Control line 4 Relay Unit 5, 6 Relay unit 10 Main line terminator 11, 12 Main line matching unit 7 Main line branch unit 8, 9 Main line branch unit e7 Branch line e1, e2, e3, e4 Information line e5, e6 Control line 13 Residential branch unit 14 Branch line terminal 15, 16 branch line matching section f7 audio signal dedicated transmission line g1, g2 video signal dedicated transmission line f1, f2, f3, f4 information line f5, f6 control line 17 doorphone with television (base unit with television) 18 audio transmission device 19 video Receiving device 20 Relay unit 21 Power receiving unit 22 Unbalanced conversion receiving unit 23 Auto gain control unit 24 Balanced transmitting unit 25a Low-pass filter unit 30 Complaint Conversion receiving unit 31 Balanced receiving unit 32 Unbalanced transmitting unit 50 Auto gain control unit 51 Half wave rectifying unit 52 Differential amplifying unit 53 Amplifying adjusting unit 75 Residential branch unit 76 Band-pass filter unit 77 Unbalanced converting receiving unit ( Non-transformer unbalanced conversion receiving unit) 78 Loop detecting unit 79 Video signal transmitting unit 80 Matching unit 81 Power receiving unit 104 Unbalanced converting receiving unit 139 Loop detecting unit 160 Video signal transmitting unit 173, 175 Amplifying capacitors 174, 176 Amplifying unit Resistors 177, 178 Transistors for switches 181, 182 Doorphone handset with camera 183 Central controller j7 Trunk j1, j2, j3, j4 Information line j5, j6 Control line 187 Trunk termination 188, 189 Trunk matching section 184 Trunk branch 185 , 186 main branch k7 branch k1, k2, k3, k Information line k5, k6 control line 190 dwell unit branch unit 191,192 branch line branching unit 193 branch line termination unit 194,195 branch line matching unit l7 audio signal dedicated transmission line g1, g2 video signal dedicated transmission line l1, l2, l3, l4 information line l5, l6 Control line 196 Door phone with TV 197 Audio transmitter 198 Video receiver

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 3/36 H04J 1/10 H03H 11/32 H04M 9/00

Claims (5)

(57) [Claims] 1. A plurality of slave units with a camera, a trunk line or a branch line connected to the slave units with a camera, a branch unit connected to the trunk line or a branch line, and a branch unit connected to the branch unit. In a two-wire audio / video signal multiplex transmission system including a master unit with a television, the repeater having an amplification function provided on the trunk or branch line includes an unbalanced conversion receiving unit, an auto gain control unit, and a balanced transmission. And a two-wire audio-video signal multiplex transmission system. 2. A system for multiplexing transmission of an audio signal, a video signal modulated in a frequency band not overlapping with an audio signal frequency, and a DC current using a pair line, and an arbitrary relay point of the pair line. A connected repeater, which receives the video signal in a balanced manner, converts the video signal into an unbalanced signal, and outputs the unbalanced signal.
An unbalanced conversion receiving unit, and an automatic obtaining unit for obtaining a video signal adjusted to a predetermined transmission signal level.
A gain control unit, the video signal obtained by the auto gain control unit is converted into a balanced signal, and in a frequency band of the video signal, an output impedance equal to the characteristic impedance of the pair wire is maintained; A means for maintaining a high output impedance in the frequency band and direct current of the audio signal, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of a video signal and for transmitting both the audio signal and the direct current. Low-pass filter unit for transmitting in the direction, having means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a DC current from the pair wire, to a specific voltage level Generates and supplies power to the unbalanced conversion receiving unit, the auto gain control unit, and the balanced transmitting unit A that power receiving portion, the unbalanced conversion receiver unit passes through the video signal, the
Blocking the direct current and the audio signal,
In the frequency band, a characteristic impedance or
Is a balanced receiving means for maintaining high impedance,
Unbalanced transmission means for unbalanced conversion and output of received video signals
The auto gain control section has a
Current signal level is lower than the specified AC signal level.
Multiply the current signal level to increase the predetermined voltage level.
Rectifying means for obtaining a bias voltage,
The bias voltage obtained by the stage is
Multiplied by the increased voltage level to obtain a predetermined voltage level.
Differential amplification means for obtaining a DC voltage for increased amplification adjustment
And an amplifier for adjusting the amplification obtained by the differential amplifier.
The input AC signal is converted into a predetermined transmission signal by the
And amplifying means for amplifying the signal to a signal level . 3. A system for multiplexing transmission of an audio signal, a video signal modulated to a frequency band not overlapping with an audio signal frequency, and a DC current using a pair line, wherein the system is connected to an arbitrary relay point of the pair line. A connected repeater, which receives the video signal in a balanced manner, converts the video signal into an unbalanced signal, and outputs the unbalanced signal.
An unbalanced conversion receiving unit, and an automatic obtaining unit for obtaining a video signal adjusted to a predetermined transmission signal level.
A gain control unit, the video signal obtained by the auto gain control unit is converted into a balanced signal, and in a frequency band of the video signal, an output impedance equal to the characteristic impedance of the pair wire is maintained; A means for maintaining a high output impedance in the frequency band and direct current of the audio signal, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of a video signal and for transmitting both the audio signal and the direct current. Low-pass filter unit for transmitting in the direction, having means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a DC current from the pair wire, to a specific voltage level Generates and supplies power to the unbalanced conversion receiving unit, the auto gain control unit, and the balanced transmitting unit A that power receiving portion, the unbalanced conversion receiver unit passes through the video signal, the
Blocking the direct current and the audio signal,
The same characteristic impedance in the wire pairs in a frequency band
Is a balanced receiving means for maintaining high impedance,
Unbalanced transmission means for unbalanced conversion and output of received video signals
And the balanced receiving means passes the video signal.
A condenser for blocking passage of the direct current and the audio signal
Equal to the pair line in the video signal frequency band.
Bias to maintain neutral or high impedance
First function connected through members and having the same characteristics and performance
A dynamic electronic component and a second active electronic component, wherein the automatic gain control section
Current signal level is lower than the specified AC signal level.
Multiply the current signal level to increase the predetermined voltage level.
Rectifying means for obtaining a bias voltage,
The bias voltage obtained by the stage is
Multiplied by the increased voltage level to obtain a predetermined voltage level.
Differential amplification means for obtaining a DC voltage for increased amplification adjustment
And a DC for amplification degree adjustment obtained by the differential amplification means.
The input AC signal is converted into a predetermined transmission signal by a voltage.
A repeater comprising: amplification adjustment means for amplifying to a level . 4. A system for multiplexing transmission of an audio signal, a video signal modulated in a frequency band not overlapping with an audio signal frequency, and a DC current using a pair line, wherein the system is connected to an arbitrary relay point of the pair line. A connected repeater, which receives the video signal in a balanced manner, converts the video signal into an unbalanced signal, and outputs the unbalanced signal.
An unbalanced conversion receiving unit, and an automatic obtaining unit for obtaining a video signal adjusted to a predetermined transmission signal level.
A gain control unit, the video signal obtained by the auto gain control unit is converted into a balanced signal, and in a frequency band of the video signal, an output impedance equal to the characteristic impedance of the pair wire is maintained; A means for maintaining a high output impedance in the frequency band and direct current of the audio signal, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of a video signal and for transmitting both the audio signal and the direct current. Low-pass filter unit for transmitting in the direction, having means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a DC current from the pair wire, to a specific voltage level Generates and supplies power to the unbalanced conversion receiving unit, the auto gain control unit, and the balanced transmitting unit A that power receiving portion, the unbalanced conversion receiver unit passes through the video signal, the
Blocking the direct current and the audio signal,
In the frequency band, a characteristic impedance or
Is a balanced receiving means for maintaining high impedance,
Unbalanced transmission means for unbalanced conversion and output of received video signals
Wherein the unbalanced transmitting means comprises a first active electronic unit.
The video signal output from the product or the second active electronic component
Signal with high input impedance receiving means and output
The automatic gain control section has an unbalanced output active electronic component for
Current signal level is lower than the specified AC signal level.
Multiply the current signal level to increase the predetermined voltage level.
Rectifying means for obtaining a bias voltage,
The bias voltage obtained by the stage is
Multiplied by the increased voltage level to obtain a predetermined voltage level.
Differential amplification means for obtaining a DC voltage for increased amplification adjustment
And an amplifier for adjusting the amplification obtained by the differential amplifier.
The input AC signal is converted into a predetermined transmission signal by the
And amplifying means for amplifying the signal to a signal level . 5. A system for multiplexing transmission of an audio signal, a video signal modulated in a frequency band not overlapping with an audio signal frequency, and a DC current using a pair line, wherein the system is connected to an arbitrary relay point of the pair line. A connected repeater, which receives the video signal in a balanced manner, converts the video signal into an unbalanced signal, and outputs the unbalanced signal.
An unbalanced conversion receiving unit, and an automatic obtaining unit for obtaining a video signal adjusted to a predetermined transmission signal level.
A gain control unit, the video signal obtained by the auto gain control unit is converted into a balanced signal, and in a frequency band of the video signal, an output impedance equal to the characteristic impedance of the pair wire is maintained; A means for maintaining a high output impedance in the frequency band and direct current of the audio signal, comprising a balanced transmitting section for transmitting to the pair wire, and a coil, for preventing the passage of a video signal and for transmitting both the audio signal and the direct current. Low-pass filter unit for transmitting in the direction, having means for maintaining a high input impedance in the frequency band of the video signal and the frequency band of the audio signal, receiving a DC current from the pair wire, to a specific voltage level Generates and supplies power to the unbalanced conversion receiving unit, the auto gain control unit, and the balanced transmitting unit A that power receiving portion, the unbalanced conversion receiver unit passes through the video signal, the
Blocking the direct current and the audio signal,
In the frequency band, a characteristic impedance or
Is a balanced receiving means for maintaining high impedance,
Unbalanced transmission means for unbalanced conversion and output of received video signals
And the balanced receiving means passes the video signal.
A condenser for blocking passage of the direct current and the audio signal
Equal to the pair line in the video signal frequency band.
Bias to maintain neutral or high impedance
First function connected through members and having the same characteristics and performance
Having a dynamic electronic component and a second active electronic component,
The unbalanced transmitting means is provided for the first active electronic component or the second function.
The video signal output from the moving electronic component is
Unbalanced output receiving and outputting with impedance receiving means
Active electronic components, and the auto gain control section
Current signal level is lower than the specified AC signal level.
Multiply the current signal level to increase the predetermined voltage level.
Rectifying means for obtaining a bias voltage,
The bias voltage obtained by the stage is
Multiplied by the increased voltage level to obtain a predetermined voltage level.
Differential amplification means for obtaining a DC voltage for increased amplification adjustment
And a DC for amplification degree adjustment obtained by the differential amplification means.
The input AC signal is converted into a predetermined transmission signal by a voltage.
A repeater comprising: amplification adjustment means for amplifying to a level .