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TDM and FDM telephone communication

  • US 4,013,840 A
  • Filed: 07/11/1975
  • Issued: 03/22/1977
  • Est. Priority Date: 05/15/1972
  • Status: Expired due to Term
First Claim
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1. A random access communication system for a plurality of telephone sets comprising:

  • a data processor;

    common cabling for communicating frequency multiplexed amplitude modulated signals between said telephone sets and control signals between said telephone sets and said data processor;

    means for coupling said processor and said sets to said cabling;

    a plurality of said telephone sets, each of said telephone sets comprising;

    a transmitter for transmitting a carrier signal over said cabling to other telephone sets, each said transmitter comprising an adjustable source of said carrier signals to transmit selected carrier signals and means to amplitude modulate the carrier signal transmitted by said transmitter,a receiver for receiving a carrier signal over said cabling from other telephone sets, each said receiver being pre-tuned to receive only one carrier signal which differs for each telephone set and is dedicated thereto and means to amplitude demodulate the carrier signal received by said receiver, andmeans for initiating a call to a called telephone set comprising means responsive to pulse code groups which are included in said control signals for digitally adjusting the frequency of the carrier signal of the transmitter associated with a calling telephone set to the dedicated carrier signal associated with the receiver of the called telephone set and adjusting the frequency of the carrier signal of the transmitter associated with the called set to the dedicated carrier signal associated with the receiver of the calling set; and

    wherein said data processor responds to said means for initiating a call by transmitting pulse code groups which are included in said control signals indentifying the called and calling telephone sets to said calling and called sets respectively, and wherein said control signals are transmitted in time division multiplex format.

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