Multiplexed audio-video signal transmission system through pair-wire
First Claim
1. A multiplexed audio-video signal transmission system for transmitting a multiplexed audio-video signal and DC power through a wire-pair, in which a video signal modulated to a predetermined frequency band does not overlap a frequency band of an audio signal said audio signal and said video signal being carried in said wire-pair in opposite phase in a balanced condition, and said DC power being carried between said wire-pair, said multiplexed audio-video signal transmission system comprising:
- camera-equipped subunit means having a camera, a speaker and a microphone for producing a first balanced audio-video signal;
first wire-pair means connected to said subunit means for transmitting said first balanced audio-video signal;
a relay device connected to said first wire-pair means, said relay device separating a balanced video signal from said first balanced audio-video signal to refine said balanced video signal and for combining said refined balanced video signal with a separated audio signal to produce a second balanced audio-video signal, said relay device comprising;
(i) a balanced-to-imbalanced convertor for converting said separated balanced video signal to an unbalanced video signal;
(ii) an aromatic gain control unit for amplifying said unbalanced video signal;
and(iii) a balanced transmitter for producing an amplified balanced video signal which is a refined version of said balanced video signal;
second wire-pair means connected to said relay device for transmitting said second balanced audio-video signal;
a door branching device connected to said second wire-pair means for receiving said second balanced audio-video signal and for separating said audio signal and said video signal; and
a television-equipped control unit connected to said door branching device for viewing an image captured by said camera using said video signal and for effecting a two-way communication with said camera-equipped subunit means using said audio signal.
1 Assignment
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Accused Products
Abstract
A multiplexed audio-video signal transmission system has a camera-equipped intercom which produces a balanced audio-video signal. A twisted pair-wire connected to the intercom transmits a multiplexed signal of audio signal, video signal modulated to a frequency band not overlapping the audio signal frequency, and DC power. The audio signal and video signal are carried in the pair-wire in opposite phase in a balanced condition, and the DC power is carried between the pair-wire. A relay device is inserted in the pair-wire to refine the video signal. Main line branching device and door branching device are provided to branch out the multiplexed signal to a television equipped control unit 17.
102 Citations
22 Claims
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1. A multiplexed audio-video signal transmission system for transmitting a multiplexed audio-video signal and DC power through a wire-pair, in which a video signal modulated to a predetermined frequency band does not overlap a frequency band of an audio signal said audio signal and said video signal being carried in said wire-pair in opposite phase in a balanced condition, and said DC power being carried between said wire-pair, said multiplexed audio-video signal transmission system comprising:
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camera-equipped subunit means having a camera, a speaker and a microphone for producing a first balanced audio-video signal; first wire-pair means connected to said subunit means for transmitting said first balanced audio-video signal; a relay device connected to said first wire-pair means, said relay device separating a balanced video signal from said first balanced audio-video signal to refine said balanced video signal and for combining said refined balanced video signal with a separated audio signal to produce a second balanced audio-video signal, said relay device comprising; (i) a balanced-to-imbalanced convertor for converting said separated balanced video signal to an unbalanced video signal; (ii) an aromatic gain control unit for amplifying said unbalanced video signal; and (iii) a balanced transmitter for producing an amplified balanced video signal which is a refined version of said balanced video signal; second wire-pair means connected to said relay device for transmitting said second balanced audio-video signal; a door branching device connected to said second wire-pair means for receiving said second balanced audio-video signal and for separating said audio signal and said video signal; and a television-equipped control unit connected to said door branching device for viewing an image captured by said camera using said video signal and for effecting a two-way communication with said camera-equipped subunit means using said audio signal. - View Dependent Claims (2, 3, 4, 5, 6, 10, 11, 12)
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7. A multiplexed audio-video signal transmission system for transmitting a multiplexed audio signal video signal and electrical power through a wire-pair, in which a video signal modulated to a predetermined frequency band does not overlap a frequency band of an audio signal, said audio signal and said video signal being carried in said wire-pair in opposite phase in a balanced condition, and said electrical power being carried between said wire-pair, said multiplexed audio-video signal transmission system comprising:
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camera-equipped subunit means having a camera, a speaker and a microphone for producing a first balanced audio-video signal; first wire-pair means connected to said subunit means for transmitting said first balanced audio-video signal; a relay device connected to said first wire-pair means, said relay device separating a balanced video signal from said first balanced audio-video signal to refine said balanced video signal and for combining said refined balanced video signal with a separated audio signal to produce a second balanced audio-video signal, said relay device comprising; (i) a balanced-to-unbalanced converter that converts said separated balanced video signal to an unbalanced video signal; (ii) an automatic gain control unit that amplifies said unbalanced video signal; and (iii) a balanced transmitter that produces an amplified balanced video signal which is a refined version of said balanced video signal; second wire-pair means connected to said relay device for transmitting said second balanced audio-video signal; a line branching device connected to said second wire-pair means that receives and refines said second balanced audio-video signal and for producing a third balanced audio-video signal; third wire-pair means connected to said branching device for transmitting said third balanced audio-video signal; a door branching device connected to said third wire-pair means for receiving said third balanced audio-video signal and for separating said audio signal and said video signal; and a television-equipped control unit connected to said door branching device for viewing an image captured by said camera using said video signal and for effecting a two-way communication with said camera-equipped subunit means using said audio signal. - View Dependent Claims (8, 9)
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13. A balanced-to-unbalanced converter used in a system for transmitting through a wire-pair a multiplexed audio signal, a video signal modulated to a frequency band that does not overlap an audio signal frequency, and electrical power, said audio signal and said video signal being carried in said wire-pair in an opposite phase in a balanced condition, and said electrical power being carried between said wire-pair, said balanced-to-unbalanced converter, comprising:
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a balanced receiver having an impedance matching element to present an impedance equal to said wire-pair at said video signal frequency band for blocking said electrical power and said audio signal, and for passing said video signal; and an unbalanced transmitter for removing same-phase signal components from said balanced video signal, applying a balanced-to-unbalanced signal conversion, and producing said unbalanced signal. - View Dependent Claims (14, 15)
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16. A relay device used with a wire-pair for transmitting a multiplexed audio signal, a video signal modulated to a frequency band that does not overlap an audio signal frequency, and an electrical current, said audio signal and said video signal being carried by said wire-pair, in opposite phase in a balanced condition, said electrical current being carried between said wire-pair, said relay device comprising:
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I. a balanced-to-unbalanced converter, comprising; (i) a balanced receiver having an impedance matching element to present an impedance equal to said wire-pair at said video signal frequency band, said impedance matching element blocking said electrical current and said audio signal while passing said balanced video signal; and (ii) an unbalanced transmitter that removes same-phase signal components from said balanced video signal, applies a balanced-to-unbalanced signal conversion, and produces an unbalanced video signal; II. an automatic gain control device that adjusts a gain of said unbalanced video signal to a predetermined transmission signal level and outputs a level-adjusted signal, said automatic gain control unit comprising; (i) a half-wave rectification circuit that half-wave rectifies and smooths said unbalanced video signal and produces a bias voltage; (ii) a differential amplification circuit that multiplies said bias voltage to produce an adjustment DC voltage; and (iii) an amplification adjustment circuit that amplifies said unbalanced video signal by said adjustment DC voltage; III. a balanced transmitter that converts said amplified unbalanced video signal to a refined and balanced video signal; IV. a low pass filter comprising a coil, said coil being connected in parallel to a series connection of said balanced-to-unbalanced converter, said automatic gain control device, and said balanced transmitter for blocking said video signal and bidirectionally transmitting said audio signal and said DC current, and V. a power supply unit that receives said electrical current from said wire-pair and generates a predetermined voltage which is supplied to said balanced-to-unbalanced converter, said automatic gain control device, and said balanced transmitter. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification