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Single-conductor power line communications system

  • US 4,714,912 A
  • Filed: 12/31/1986
  • Issued: 12/22/1987
  • Est. Priority Date: 12/31/1986
  • Status: Expired due to Fees
First Claim
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1. A system for communicating digital information on a power line circuit having a plurality of conductors interconnecting at least one AC power source and at least one power-consuming load, comprising:

  • at least one means, coupled to at least one of the conductors, for receiving a PLC signal and for controlling at least one controlled-power-consumption load responsive to the information received; and

    at least one transmitter for forming the PLC signal by injection of a PLC signal current in series with only a single one of the power line conductors, and comprising;

    input means for receiving digital information to be transmitted;

    generator means for providing an output signal with (1) cyclic alternation between first and second states at a PLC frequency, at least two orders of magnitude greater than the AC source frequency, responsive to a first condition of the digital information at said input means, and (2) another selection of at least the second state, responsive to a second condition of the digital information at said input means;

    switching means for providing a controllable impedance with respective low impedance and high impedance states responsive to respective first and second states of said output signal; and

    saturable means for effectively coupling the switching means to the single conductor for injecting the PLC signal current therein only when the current in the single conductor is not greater than a saturation current level.

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