COMMUNICATION SYSTEM HAVING SIGNAL STORAGE
First Claim
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1. A graphic communication system comprising:
- transmitter means for generating variable frequency modulated data signals in the order of 3,000 Hz. and below representative of graphic intelligence, receiver means receptive of said data signals and operable to graphically reproduce the intelligence represented thereby, recorder means for magnetically recording said data signal intelligence on a moving magnetic recording medium and capable of introducing frequency deviations in signals recorded thereby, and compensator means in circuit with said transmitter means, recorder means and said receiver means for correctively minimizing recorder introduced deviations in signals recorded by said recorder means prior to reproduction of intelligence therefrom by said receiver means, said compensator means comprising heterodyne circuit means for modulating said data signals to subnormal frequencies prior to introducing the same to said recorder means, and additional heterodyne circuit means for modulating signals recorded by said recorder means to original data signal frequencies prior to introducing the same to said receiver means whereby the recorder introduced errors therein are maintained at subnormal values proportional to said subnormal frequencies.
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Abstract
A communication system in which frequency-modulated intelligence signals are stored on magnetic tape for subsequent retransmission to one or more receivers. Errors in the recorded signals, introduced by inherent defects of the recording mechanism, are effectively compensated by recording subnormal frequency signals derived from the intelligence signals. During playback the recorded signals are reconverted to original frequencies for transmission to the receiver.
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Citations
2 Claims
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1. A graphic communication system comprising:
- transmitter means for generating variable frequency modulated data signals in the order of 3,000 Hz. and below representative of graphic intelligence, receiver means receptive of said data signals and operable to graphically reproduce the intelligence represented thereby, recorder means for magnetically recording said data signal intelligence on a moving magnetic recording medium and capable of introducing frequency deviations in signals recorded thereby, and compensator means in circuit with said transmitter means, recorder means and said receiver means for correctively minimizing recorder introduced deviations in signals recorded by said recorder means prior to reproduction of intelligence therefrom by said receiver means, said compensator means comprising heterodyne circuit means for modulating said data signals to subnormal frequencies prior to introducing the same to said recorder means, and additional heterodyne circuit means for modulating signals recorded by said recorder means to original data signal frequencies prior to introducing the same to said receiver means whereby the recorder introduced errors therein are maintained at subnormal values proportional to said subnormal frequencies.
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2. The combination of claim 1, wherein said transmitter means generates separate X- and Y-coordinate data signals, and said compensator means separates said X- and Y-data signals and operatively modulates the same by respectively mixing the same with fixed frequency signals to produce said recording signals therefrom and by mixing the latter with said fixed frequency signals to produce signals of data signal frequency having minimized errors.
Specification