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Locking device for utility locks with a key signal transmitter and a key signal receiver

  • US 4,317,157 A
  • Filed: 08/30/1979
  • Issued: 02/23/1982
  • Est. Priority Date: 08/31/1978
  • Status: Expired due to Term
First Claim
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1. In a locking device for utility locks having a lock bolt;

  • wherein a key signal transmitter is disposed in a portable housing and a stationary key signal receiver is disposed in the vicinity of the lock bolt and controls the operation of the lock bolt, said transmitter having a coder for generating a predetermined code specific to the locking device, said receiver having a decoder for decoding the code generated by said coder, the improvement comprising;

    said coder comprising,an impulse generator for producing pulses at a constant pulse repetition rate, andpulse width modulation means coupled to said impulse generator for producing a key pulse upon each generation of a pulse by said impulse generator, each key pulse having a pulse width selected between predetermined limits within the period determined by the pulse repetition rate of said impulse generator, said pulse width generator producing a predetermined sequence of key pulses characterized by at least three different pulse widths; and

    said decoder comprising means for decoding the predetermined sequence of said key pulses characterized by said at least three different pulse widths.

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