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Selective test circuit for fire detectors

  • US 4,489,312 A
  • Filed: 04/14/1982
  • Issued: 12/18/1984
  • Est. Priority Date: 04/15/1981
  • Status: Expired due to Term
First Claim
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1. A circuit for selectively testing detectors connected between one of a plurality of alarming lines each extending from a section relay of a receiving unit and a common line comprising:

  • an address-signal-sensing circuit for producing a coincidence signal when coincidence is sensed between an address signal transmitted through the alarming line and the inherent address code allotted to each fire detector beforehand;

    a test-voltage-generating circuit for generating a test voltage to be applied to each fire detector in response to said coincidence signal;

    a serial connection of a first Zenner diode and a condenser connected between the alarming line and the common line; and

    means for generating a resetting signal to reset the address-signal-sensing circuit and the test-voltage-generating circuit when the alarming line voltage is in excess of a predetermined value;

    whereby the condenser is charged at a voltage exceeding a predetermined value and, at the same time, resets the address-signal-sensing circuit and the test-voltage-generating circuit; and

    the voltage charged on the condenser acts as the power source for actuating the address-signal-sensing circuit and the test-voltage-generating circuit.

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