JP2826437B2 - Transformerless switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video and audio transmission system typified by a door phone system using a pair of wires, and performs point-to-multipoint transmission of multiplexed video and audio signals using a pair of wires. The present invention relates to a trunk branch unit and a branch line branch unit that can be performed in a point connection mode.

[0002]

2. Description of the Related Art FIG. 3 is a configuration diagram showing an example of a connection form of a video / audio transmission system represented by a door phone system.

[0003] In FIG. 3, a video / audio transmission system includes a camera-equipped audio terminal 1, typically a camera door phone, for multiplexing transmission of a video signal and a DC current which are modulated to a frequency band not overlapping with the frequency of the audio signal. Also, an audio terminal 17 with a television, which is represented by a television doorphone and has an audio transmission device 15 for supplying a direct current and transmitting an audio signal, and a video reception device 16 for receiving a video signal, is provided. The camera-equipped audio terminal 1 includes a specific pair of trunk-owned pair lines 2a and 2b among trunk lines composed of a plurality of pair lines, and a specific pair of branch lines among branch lines composed of a plurality of pair lines. Own pair wire 7a,
7b, the transmission lines 13a, 13b dedicated to audio signals and the transmission lines 14a, 14b dedicated to video signals (in FIG. 3, only one pair of the trunk line and the branch line is shown).

The above-mentioned trunk line owned pair lines 2a and 2b and the branch line owned pair lines 7a and 7b are connected via the trunk line branching unit 5, and are connected to the branch line owned pair lines 7a and 7b and the audio signal exclusive transmission line. 13a and 13b and a transmission line 14a dedicated to a video signal,
14b is connected via the branch line branching device 10. At the end of the main line pair 2a, 2b, there is a main line terminator 4 that matches the characteristic impedance of the main lines 2a, 2b in the frequency band of the video signal and has a higher impedance characteristic in the lower frequency band than the video signal. A branch line having a characteristic impedance of the branch lines 7a and 7b in the frequency band of the video signal and having a higher impedance characteristic in a lower frequency band than the video signal is provided at a terminating end of the pair line 7a and 7b. A terminator 8 is provided.

Here, the main branch unit 5 is composed of the main trunks 2a and 2b.
, And one end of each of the branch lines 7a and 7b, and allows the audio signal to pass through the branch lines 7a and 7b,
a, 3b, and receives a DC signal from the terminal 3a,
3b, the signal is balanced and received with high input impedance, and in the frequency band of the video signal, the signal is balanced and transmitted to the terminals 6a, 6b with the output impedance matched with the branch lines 7a, 7b.

[0006] The branch line branching device 10 includes branch lines 7a and 7a.
b, and is connected between the audio signal dedicated transmission lines 13a, 13b and the end of the video signal dedicated transmission lines 14a, 14b, receives DC current from the terminals 11a, 11b, and The audio signal is bidirectionally transmitted between the terminal 9b and the terminals 11a and 11b, and the video signal is received in a balanced manner with high input impedance from the terminals 9a and 9b, and matched with the video signal dedicated transmission lines 14a and 14b in the frequency band of the video signal. Unbalanced transmission is performed to the terminals 12a and 12b with the obtained output impedance.

Conventionally, the main branch 5 and the branch 10 of the video / audio transmission system configured as described above are
The one using a transformer is used.

FIG. 4 is a circuit diagram showing the configuration of a conventional transformer trunk branch unit. The transformer main branch unit 72 includes a balanced transmission unit 73 for transmitting a video signal and a low-band signal mixing unit 74 for transmitting an audio signal.
5b corresponds to the terminals 3a and 3b in FIG.
9b corresponds to the terminals 6a and 6b in FIG.

In one balanced transmission section 73, terminals 75a,
The video signal input to 75b is supplied to the condenser 76a,
76b, terminals 79a, 79a,
79b, and is supplied to the input side winding of a transformer 77 having an output impedance that is matched with the characteristic impedance of the branch line owned pair.
7 is output to terminals 79a and 79b via capacitors 78a and 78b. At this time, the passage of the audio signal and the DC current is prevented by the capacitors 76a and 76b and the capacitors 78a and 78b.

[0010] In the other low-frequency signal mixing section 74, the audio signal is supplied to the condensers 80a and 80b and the coil 81.
a, 81b to allow bidirectional transmission between terminals 75a, 75b and terminals 79a, 79b. At this time, the coils 81a and 81b block the passage of the video signal, and the capacitors 80a and 80b block the passage of the direct current.

FIG. 5 is a circuit diagram showing a configuration of a conventional transformer branch line branching device. The transformer branch line branching device 82
An unbalanced transmission unit 84 that transmits a video signal and converts the balance into unbalanced; and a low-band signal separation unit 8 that transmits an audio signal.
3 and terminals 85a and 85b are terminals 9 in FIG.
a, 9b, and the terminals 88a, 88b are the terminals 1 in FIG.
The terminals 91a and 91b correspond to the terminals 12a and 12b in FIG.

In one unbalanced transmission section 84, a terminal 85
a, 85b are supplied to the capacitors 89a, 89b and the terminals 9 with high input impedance.
1a and 91b, which pass through a transformer 90 which has an output impedance unmatched and has a characteristic of an output impedance matched with the characteristic impedance of a video signal transmission line typified by coaxial, and outputs from terminals 91a and 91b. I do. At this time, the audio signal and the DC current are
The passage is blocked by a and 89b.

In the other low-band signal separation section 83, the audio signal is converted into coils 86a and 86b and a capacitor 87.
a, 87b to allow bidirectional transmission between terminals 85a, 85b and terminals 88a, 88b. At this time, the coils 86a and 86b block the passage of the video signal, and the capacitors 87a and 87b block the passage of the direct current.

[0014]

However, in the main branch and branch lines using the conventional transformers as described above, a transformer having a uniform high input impedance characteristic in a frequency band of a video signal is required. Nevertheless, it is technically difficult to produce the required transformer. Therefore, a transformer having a non-uniform high input impedance characteristic in the frequency band of the video signal has to be used, which causes a deterioration in transmission 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, the transmission signal level is reduced when the video signal passes.

Further, since the cost of the transformer is increased,
This leads to an increase in the cost of the entire system.

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

That is, the conventional main line branching device and branch line branching device using a transformer have the above-mentioned problems.

According to the present invention, in consideration of such problems of the conventional branching device, uniform high input impedance characteristics can be ensured in a frequency band of a video signal, and a decrease in a transmission signal level when the video signal passes is prevented. It is an object of the present invention to provide a transformerless branching device that can prevent the occurrence of a failure, reduce the cost of the entire system, and reduce the size and weight of the main body.

[0020]

According to the first aspect of the present invention, an audio signal, a video signal modulated in a frequency band not overlapping with the audio signal frequency, and a DC current are multiplex-transmitted by using a pair of trunk lines. A transformerless branching device used in a system, in which a high-impedance bias member is connected to an arbitrary point of a main line via a capacitor that passes a frequency band of a video signal, and is transmitted from the main line. A balanced receiving section that blocks the passage of audio signals and DC current and receives balanced video signals, and a pair of branch lines that pass the frequency band of video signals and have high impedance in the frequency band of audio signals and DC current Through a capacitor having the following characteristics, a matching member matched with the characteristic impedance of the pair of branch lines in the frequency band of the video signal is connected, A balanced transmission unit for balanced transmission of a received video signal to a pair of branch lines, and an electron connected between the pair of trunk lines and the pair of branch lines and having low impedance characteristics in the frequency band of the audio signal. A transformerless branching device for a trunk line, comprising a member, and a low-frequency signal mixing unit that blocks passage of a video signal and a DC current and bidirectionally transmits an audio signal.

According to a third aspect of the present invention, there is provided a transformer for use in a system for multiplex transmission of an audio signal, a video signal modulated in a frequency band not overlapping with the audio signal frequency, and a DC current using a pair of branch lines. A high-impedance bias member is connected to an arbitrary point of a pair of branch lines via a capacitor that passes a frequency band of a video signal, and a sound signal transmitted from the pair of branch lines. A balanced receiving unit that blocks the passage of DC current and receives balanced video signals, an unbalanced converting unit that converts unbalanced video signals received by active electronic components such as transistors and FETs, and dedicated video signals A matching member matched to the video signal transmission line in the video signal frequency band is connected to the transmission line via a capacitor that passes the video signal frequency band. An unbalanced transmission unit for transmitting the unbalanced converted video signal, and an electronic member connected between the pair of branch lines and the transmission line dedicated to the audio signal and having a characteristic of low impedance in the frequency band of the audio signal. A transformerless branching unit for a branch line, comprising: a low-band signal separating unit for blocking a passage of a video signal and a direct current and transmitting a sound signal bidirectionally.

[0022]

According to the present invention, a balanced receiving section receives a video signal in a balanced manner by blocking the passage of an audio signal and a DC current transmitted from a pair of trunk lines, and a balanced transmitting section converts the balanced received video signal. The balanced signal is transmitted to the pair of branch lines, and the low-frequency signal mixing unit blocks the passage of the video signal and the DC current and bidirectionally transmits the audio signal.

Also, in the present invention, the balanced receiving section receives the video signal in a balanced manner by preventing the passage of the audio signal and the DC current transmitted from the pair of branch lines, and the unbalanced converting section performs the balanced receiving. Unbalanced conversion of the video signal, the unbalanced transmission unit transmits the unbalanced converted video signal to the video signal dedicated transmission line,
The low-frequency signal separation unit transmits the audio signal bidirectionally while blocking the passage of the video signal and the DC current.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing embodiments thereof.

FIG. 1 is a circuit diagram of a trunkless transformerless branching device according to an embodiment of the present invention. Here, the connection form of the video / audio transmission system represented by the door phone system is the same as the example shown in FIG. 3 described above, and the description of the entire video / audio transmission system will be omitted. That is, the transformerless main branch unit 18 of FIG. 1 is provided as the main branch unit 5 of FIG.
a and 23b correspond to 3a and 3b in FIG.
Reference numeral 39b corresponds to 6a and 6b in FIG.

The transformerless trunk line splitter 18 receives a balanced video signal inputted to a pair of trunk line pairs with a high input impedance, and a balanced transmission by matching the characteristic impedance of the branch line pair line. Transmitting section 20, a low-frequency signal mixing section 21 for performing two-way transmission of audio signals, and a DC current received from a mains-owned pair line is converted into a DC voltage, and the DC voltage is converted into a balanced receiving section 19 and a balanced transmitting section. The power receiving unit 22 is configured to supply power to the power receiving unit 20.

The above-mentioned balanced receiving section 19 passes the bias resistors 26a, 27a, 26b, 27b, which hold an impedance sufficiently larger than the characteristic impedance in the video signal frequency band of the pair of main-line pair wires, and the video signal frequency band. FET 28a to which capacitors 25a and 25b, a source resistor 30a and an amplifying capacitor 31a are connected in parallel, and a drain resistor 29a is connected.
And a source resistor 30b and an amplifying capacitor 31b
Are connected in parallel, and the FET 28b is connected to the drain resistor 29b.

The balanced transmitting section 20 includes FETs 35a, 3
5b, a capacitor 32a connected to the gate of the FET 35a, bias resistors 33a, 34a, and the FET 35b
32b, bias resistors 33b and 34b, the source of the FET 35a and the terminal 39
a, and a matching resistor 37a for matching with the characteristic impedance of the branch line owned pair wire connected to the terminals 39a and 39b, and a capacitor 3 for passing the video signal.
8a, a matching resistor 37b that is connected between the source of the FET 35b and the terminal 39b and matches the characteristic impedance of the branch line owned pair wire connected to the terminals 39a and 39b, a capacitor 38b that passes a video signal, and a FET 3
5a and a source resistor 36a connected to the source
The video signal composed of the source resistor 36b connected to the source of the T35b and output balanced by the balanced receiving unit 19 is balanced and transmitted with the characteristic impedance of the branch line owned pair line connected to the terminals 39a and 39b. .

The low-frequency signal mixing section 21 includes a capacitor 40a connected between the terminal 23a and the terminal 39a for passing the audio signal, a coil 41a for passing the audio signal and blocking the video signal, and a terminal. 23b and terminal 39b
And a coil 41b that allows the audio signal to pass and blocks the video signal and prevents the video signal from passing therethrough. Both the audio signals pass between the terminals 23a and 23b and the terminals 39a and 39b. Directional transmission. Here, the condensers 40a and 40b and the coil 4
1a and 41b are electronic members.

Next, the operation of the transformerless trunk line splitter 18 of the above embodiment will be described.

First, the bias resistors 26a, 27a and 26b, 27b provided in the balanced receiving section 19 maintain a uniform high input impedance in the frequency band of the video signal. It is possible to avoid the deterioration of the transmission quality represented by the phase distortion.

The terminals 3 are connected by matching resistors 37a and 37b.
Matching can be achieved with a uniform output impedance in the frequency band of the video signal and the branch line splitters connected to 9a and 39b. When transmitting the video signal, the transformer is typified by phase distortion which is difficult to take measures against in the transformer. Deterioration of transmission quality can be avoided.

Also, terminals 23a, 23b are used as amplifying capacitors 31a, 31b provided in the balanced receiving section 19.
Signal level of the video signal inputted to the terminal 39a,
By using a transmission signal level of the video signal output from the 39b, the transmission signal level can be prevented from lowering due to the difference in the turns ratio between the input and output coils due to the transformer. .

In the frequency band of the audio signal, the capacitors 25a, 25b and the capacitors 38a, 38
8b, between terminals 23a and 23b and between terminals 39a and 3b.
The AC impedance between the terminals 9b 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.

Here, a plurality of transformerless trunk branching devices 18 are connected to a pair of trunk-owned pair wires for transmitting audio signals, video signals, and DC current at arbitrary locations.

FIG. 2 is a circuit diagram of a transformerless branching device for a branch line according to another embodiment of the present invention. That is,
3 is provided as the branch line branching device 10 in FIG. 3, and the terminals 48a and 48b of the transformerless branch line branching device 42 correspond to 9a and 9b in FIG. 70b corresponds to 12a and 12b in FIG. 3, and terminals 71a and 71b correspond to 11a and 11b in FIG.

The transformer-less branch line branching unit 42 includes a balanced receiving unit 43 that receives a video signal balanced and input to a pair of branch lines with a high input impedance and converts the video signal from balanced to unbalanced. A balanced conversion section 44, an unbalanced transmission section 45 for amplifying and transmitting a video signal, a low-frequency signal separation section 46 for performing bidirectional transmission of an audio signal, and terminals 71a,
The power receiving section 47 is configured to receive a DC current supplied from 71b, generate a predetermined DC voltage, and supply the DC voltage to the balanced receiving section 43 and the unbalanced transmitting section 45.

The above-mentioned balanced receiving section 43 passes through the bias resistors 51a, 52a, 51b, 52b that hold an impedance sufficiently larger than the characteristic impedance of the pair of branch line owned pair wires in the video signal frequency band, and passes through the video signal frequency band. FETs 53 to which capacitors 50a and 50b to be connected, a drain resistor 56 are connected, and a source resistor 58
And a FET 54 connected in parallel with a capacitor 57 having a sufficiently small AC impedance characteristic in the frequency band of the video signal, and a source resistor 55 shared by the FET 53 and the FET 54.
The video signal which is balanced and input to the pair of branch lines owned by the pair 48b is received with high input impedance.

The unbalance converter 44 is composed of a transistor 59 in which the drain and the emitter of the FET 53 and the drain and the base of the FET 54 are directly connected to each other, and the collector of which is connected to the collector resistor 60. A bias voltage is input to the video signal and the base, and an unbalanced video signal is output from the collector.

In the unbalanced transmitting section 45, the emitter resistor 63b is connected to the emitter, and the amplifying capacitor 66 and the amplifying resistor 67 connected in series are connected in parallel, so that the impedance is matched with the characteristic impedance in the frequency band of the video signal. The transistor 65 having the collector resistor 63a connected to the collector, the capacitor 61 for passing the frequency band of the video signal connected between the collector of the transistor 59 and the base of the transistor 65, and the transistor 6
5, a bias resistor 62a, 62b and a capacitor 64 connected between the terminal 70a and the collector of the transistor 65 for passing the frequency band of the video signal. The video signal inputted from the terminals 48a, 48b is The signal is amplified to a signal level equal to the received signal level and transmitted from terminals 70a and 70b.

The low-band signal separating section 46 blocks coils 68a and 68b that block the passage of the frequency band of the video signal and the passage of the frequency band of the audio signal, and block the passage of the direct current, thereby reducing the frequency of the audio signal. It is composed of capacitors 69a and 69b that pass the band, and enables bidirectional transmission of audio signals between the terminals 48a and 48b and the terminals 71a and 71b. Here, the capacitors 69a and 69b and the coils 68a and 68b are electronic members.

Next, the operation of the transformerless branch line branching unit 42 of the above embodiment will be described.

First, the bias resistors 51a, 52a and 51b, 52b provided in the balanced receiving section 43 maintain a uniform high input impedance in the frequency band of the video signal. It is possible to avoid the deterioration of the transmission quality represented by the phase distortion.

The video signal balanced and received by the balanced receiving unit 43 is converted into unbalanced by the unbalance converting unit 44,
The collector resistance 63a can match the transmission line dedicated to the video signal connected to the terminals 70a and 70b with a uniform output impedance in the frequency band of the video signal, and it is difficult to take measures with the transformer when transmitting the video signal. It is possible to avoid transmission deterioration represented by phase distortion.

The terminal 48 is used as an amplifying capacitor 66 and an amplifying resistor 67 provided in the unbalanced transmitting section 45.
a, the received signal level of the video signal input to 48b,
By using a characteristic that maintains the transmission signal levels of the video signals output from the terminals 70a and 70b equal to each other, it is possible to avoid a decrease in the level of the transmission signal caused by a difference in the turns ratio of the input and output coils due to the transformer. can do.

In the audio signal frequency band, the AC impedance between the terminals 48a and 48b and between the terminals 71a and 71b can be kept high by the capacitors 50a and 50b. Can be avoided.

Here, a plurality of transformerless branch line splitters 42 are connected to a pair of branch line owned pair lines for transmitting audio signals and video signals at arbitrary locations.

As described above, in the main line branching device, the video signal input from the pair of main lines owned by the main line is converted into the bias resistors 26a, 27a, 26b, and 2 serving as the bias members.
The matching resistor 37, which is a matching member having balanced output with high input impedance and having output impedance characteristics matched to a pair of branch lines possessing a pair, is used.
By performing balanced transmission at a and 37b, video transmission can be realized without using a balanced transmission element such as a transformer. At a high frequency represented by the frequency band of a video signal, it is difficult to manufacture a transformer technically and costly. It facilitates the realization of a uniform high input impedance characteristic, further reduces transmission quality degradation of the video signal, and has an amplification function to avoid a reduction in the transmission signal level when the video signal passes. Therefore, it is possible to reduce the size, weight, and cost, which cannot be realized with a transformer.

Also, in the branch line splitter, the video signal input from the pair of branch line owned pair lines is balanced and received with high input impedance by using the bias resistors 51a, 52a, 51b and 52b as bias members. Then, the balanced received video signal is converted into unbalanced by the transistor 59, and unbalanced transmission is performed by the collector resistor 63a which is a matching member having an output impedance characteristic matched to an unbalanced video signal transmission line such as coaxial. In this way, video transmission can be realized without using a balanced transmission element such as a transformer, and at a high frequency represented by the frequency band of a video signal, a uniform high input which is difficult to manufacture technically and costly with a transformer. It facilitates realization of impedance characteristics, and reduces or increases the degradation of video signal transmission quality. To avoid degradation of the transmission signal level at the time of passage of the video signal by a function, further downsizing was unattainable in trans, lighter,
The cost can be reduced.

It should be noted that the circuits shown in the above embodiments are merely examples, and if they have a circuit configuration having the same function,
It is not limited to this. Further, the combination of electronic components such as FETs and transistors is not limited to this.

In each of the above embodiments, the configuration has an amplifying function. However, the present invention is not limited to this. If the level of the video signal does not affect the practical use, no amplifying function is provided. You may. In the case of having an amplifying function, the transformerless trunk line branching unit 18 may have one or both of the balanced receiving unit 19 and the balanced transmitting unit 20. It may be provided in one or both of the balanced receiving unit 43 and the unbalanced transmitting unit 45.

In the above embodiment, the power sources of the balanced receiving section 19 and the balanced transmitting section 20 of the transformerless main branch unit 18 and the balanced receiving section 43 and the unbalanced transmitting section 45 of the transformerless branch line branch unit 42 Although the power receiving unit 22 and the power receiving unit 47 are provided and obtained from the pair of the main trunk line and the transmission line dedicated to the audio signal, a configuration in which a DC voltage is externally supplied may be used instead. Alternatively, a configuration may be adopted in which a battery or the like is incorporated in the branching device.

[0053]

As is apparent from the above description, the present invention can secure a uniform high input impedance characteristic in the frequency band of a video signal, and prevent the transmission signal level from lowering when the video signal passes. In addition, there is an advantage that the cost of the entire system can be reduced, and the size and weight of the main body can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a trunkless transformerless branching device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a transformerless branching device for a branch line according to another embodiment of the present invention.

FIG. 3 is a configuration diagram illustrating an example of a system that multiplexes and transmits an audio signal, a video signal, and a DC current.

FIG. 4 is a circuit diagram of a conventional transformer main branch unit.

FIG. 5 is a circuit diagram of a conventional transformer branch line branching device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Audio terminal with camera 2a, 2b Trunk line owned pair line 5 Trunk branch unit 7a, 7b Branch line owned pair line 10 Branch line branch unit 13a, 13b Audio signal transmission line 14a, 14b Video signal transmission line 17 TV audio terminal Reference Signs List 18 transformerless trunk branching unit 19 balanced receiving unit 20 balanced transmitting unit 21 low band signal mixing unit 42 branch line branching unit 43 balanced receiving unit 44 unbalanced converting unit 45 unbalanced transmitting unit 46 low band signal separating unit 72 transformer trunk branching unit 77, 90 transformer 82 transformer branch line branching device

Continuation of the front page (56) References JP-A-60-172810 (JP, A) JP-A-4-108210 (JP, A) JP-A-4-35212 (JP, A) JP-A-3-204214 (JP) JP-A-2-73708 (JP, A) JP-A-49-11547 (JP, A) JP-B-52-37346 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB Name) H04J 1/10 H03H 11/32 H03H 11/34 H04B 3/30

Claims (4)

(57) [Claims] 1. A transformerless branching device used in 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 of trunk lines, A high-impedance bias member is connected to an arbitrary portion of the main line via a capacitor that passes the frequency band of the video signal, and the audio signal and the DC current are transmitted from the main line. A balanced receiving unit that blocks the passage and receives the video signal in a balanced manner, and a characteristic that has a high impedance in the frequency band of the audio signal and the DC current by passing the frequency band of the video signal through a pair of branch lines. And a matching member matched with the characteristic impedance of the pair of branch lines in the frequency band of the video signal through a capacitor having A balanced transmission section for balanced transmission of the balanced received video signal to the pair of branch lines, connected between the pair of main trunks and the pair of branch lines, the frequency of the audio signal A main line, comprising: an electronic member having a low impedance characteristic in a band; a low-band signal mixing unit for blocking the passage of the video signal and the DC current and bidirectionally transmitting the audio signal. Transformerless branching device. 2. The transformerless splitter according to claim 1, wherein the balanced receiving unit and / or the balanced transmitting unit has an amplifying function capable of avoiding a decrease in a transmission signal level when the video signal passes. 3. A transformerless branching device used in 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 of branch lines. A high-impedance bias member is connected to an arbitrary point of the pair of the branch lines via a capacitor that passes a frequency band of the video signal, and the audio signal and the DC signal transmitted from the pair of the branch lines are connected to each other. A balanced receiving section that blocks passage of current and receives the video signal in a balanced manner, an unbalanced converting section that performs unbalanced conversion of the video signal that has been balanced-received by active electronic components such as transistors and FETs, A signal transmission line is matched with the video signal transmission line in the frequency band of the video signal via a capacitor that passes the frequency band of the video signal. The unbalanced matching member is connected, an unbalanced transmission unit that transmits the unbalanced converted video signal, and is connected between the pair of the branch lines and the transmission line dedicated to the audio signal, and An electronic member having a characteristic of low impedance in a frequency band, blocking the passage of the video signal and the DC current, and a low-band signal separation unit that bidirectionally transmits the audio signal, Transformerless branching device for branch lines. 4. The balanced receiving unit and / or the unbalanced transmitting unit,
4. An amplifying function capable of avoiding a decrease in transmission signal level when the video signal passes.
The transformerless branching device described.