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R. F. lockout circuit for electronic locking system

  • US 4,996,525 A
  • Filed: 11/24/1989
  • Issued: 02/26/1991
  • Est. Priority Date: 11/24/1989
  • Status: Expired due to Fees
First Claim
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1. An electronic circuit for preventing a door strike solenoid connected to an electronic control unit from being falsely energized by an electrical signal supplied thereto by said electronic control unit, said electronic control unit supplying said electrical signal in response to radio frequency signals generated by a transmitter located near said electronic control unit, said electronic control unit comprising:

  • means for receiving the radio frequency signals generated by said transmitter;

    detector circuit means having an input connected to said receiving means and an output for converting said radio frequency signals to a first direct current voltage having an amplitude indicative of the field strength of said radio frequency signals;

    means having an output for generating a reference direct current voltage;

    trigger circuit means having a first input connected to the output of said detector circuit means, a second input connected to the output of said generating means and an output for producing a second direct current voltage when the amplitude of said first direct current voltage exceeds said reference direct current voltage;

    a switching transistor having a base connected to the output of said trigger circuit means, an emitter connected to ground and a collector;

    relay circuit means having a normally closed contact connected between said electronic control unit and said door strike solenoid and a coil with one end of said coil being connected to the collector of said switching transistor and the opposite end of said coil being connected to said electronic control unit, the coil of said relay circuit means being energized by the electrical signal from said electronic control unit when said switching transistor is turned on by the second direct current voltage from said trigger circuit means, the normally closed contact of said relay circuit means being opened by said energized coil thereby preventing the electrical signal supplied by said electronic control unit from falsely energizing said door strike solenoid.

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