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Signal transmission in teaching system

  • US 4,238,893 A
  • Filed: 11/03/1978
  • Issued: 12/16/1980
  • Est. Priority Date: 11/08/1977
  • Status: Expired due to Term
First Claim
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1. A teaching system comprising a master station including at least one source of main signals in a first frequency band, a source of audio signals, a source of control signals, and signal transmission apparatus comprising means for modulating a subcarrier with said audio signals so as to provide a first auxiliary signal in a frequency band removed from said first frequency band, means for modulating a subcarrier with said control signals so as to provide a second auxiliary signal in a frequency band removed from said first frequency band and said frequency band of the first auxiliary signal, means for multiplexing said main signals and said first and second auxiliary signals so as to provide a composite signal therefrom, means for modulating a carrier of predetermined frequency with said composite signal, and transmitting means for transmitting said carrier modulated with the composite signal;

  • and at least one student station spaced from said master station and at each of which there are situated reception means tunable to said predetermined frequency of said carrier, demodulating means for obtaining said composite signal from the received modulated carrier, and filter means for separating said main, audio, and control signals from the demodulated composite signal;

    wherein said control signals from said source include a plurality of command signals each associated with a respective student station to selectively control the operation of the associated respective student station, and each said student station includes control circuitry responsive to its respective command signal so that each said student station is selectively controlled in response to said respective command signal notwithstanding that said control signals are also received by other such student stations.

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