Cancelling circuit and transmission system
First Claim
1. In a transmission system for a television telephone in which a pair of terminal devices are interconnected via a transmission path, each terminal device including means coupled to applying sound signals and image data signals to said transmission path and means coupled to receive sound signals and image data signals, to minimize cross talk of signals on the transmission path, and to enable two-directional communication in an entire frequency band usable on said transmission path or a portion thereof,the improvement wherein each terminal comprises crosstalk canceling means coupled to said transmission path, said means for applying signals to said path includes for applying said sound and image data signals to said transmission path via said crosstalk canceling means including frequency separation means connected to separate at least one of said sound signals and said image data signals into a plurality of different frequency bands for application to said transmission path, and a single side band system connected to narrow the frequency band of said image data signals for transmission on said transmission path.
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Abstract
The present invention is a transmission system in which there are provided a bridge circuit in which a balanced condition is provided in an entire frequency band usable for a wire transmission line or a portion thereof, and a cancelling circuit in which a simultaneous two-directional communication is enabled by using the same frequency or the frequency adjacent thereto, and there are provided said cancelling circuits at both terminal devices opposite to each other through a transmission line, thereby enabling said simultaneous two-directional communication.
19 Citations
6 Claims
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1. In a transmission system for a television telephone in which a pair of terminal devices are interconnected via a transmission path, each terminal device including means coupled to applying sound signals and image data signals to said transmission path and means coupled to receive sound signals and image data signals, to minimize cross talk of signals on the transmission path, and to enable two-directional communication in an entire frequency band usable on said transmission path or a portion thereof,
the improvement wherein each terminal comprises crosstalk canceling means coupled to said transmission path, said means for applying signals to said path includes for applying said sound and image data signals to said transmission path via said crosstalk canceling means including frequency separation means connected to separate at least one of said sound signals and said image data signals into a plurality of different frequency bands for application to said transmission path, and a single side band system connected to narrow the frequency band of said image data signals for transmission on said transmission path.
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5. A transmission method for a picturephone unit comprising the steps of:
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transmitting a voice signal and an image data signal using cancel circuits provided at terminal units arranged at opposite ends of a single transmission path, the transmission path being a telephone line having a frequency band that can pass a voice band; controlling the crosstalk value between transmission signals to be a minimum; simultaneously and bidirectionally transmitting said voice signal and said image data signal only through said single transmission path in different frequency ranges of a common frequency band; separating said frequency band at an arbitrary frequency into a voice signal range and an image signal range; and narrowing an occupied band width for said image data signal by use of an SSB mode so as to ensure a voice signal transmission band.
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6. A transmission method for a picturephone unit comprising the steps of:
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transmitting a voice signal and an image data signal using cancel circuits provided at terminal units arranged at opposite ends of a single transmission path, the transmission path being a telephone line having a frequency band that can pass a voice band; controlling the crosstalk value between transmission signals to be a minimum; simultaneously and bidirectionally transmitting said voice signal and said image data signal only through said single transmission path in different frequency ranges of a common frequency band in a part of a transmissible frequency band; separating said frequency band at an arbitrary frequency into a voice signal range and an image signal range; and narrowing an occupied band width for said image data signal by use of an SSB mode so as to ensure a voice signal transmission band.
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Specification