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Interface for a supervised multi-input audible warning system

  • US 5,293,155 A
  • Filed: 04/10/1991
  • Issued: 03/08/1994
  • Est. Priority Date: 05/07/1990
  • Status: Expired due to Term
First Claim
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1. An interface for selectively transmitting via a plurality of interface circuits a plurality of signals from a power source to a common circuit, said common circuit being used for driving an alarm, each interface circuit comprising:

  • means for coupling the interface circuit to a power source between a positive node and a negative node of said coupling means;

    supervising means electrically connected in parallel across the coupling means between said positive and negative nodes for supervising the interface circuit for electrical faults;

    switching means, having an input through which current flows, electrically connected in parallel across the coupling means between said positive and negative nodes, and an output, said output having a first output node and a second output node, for reversing said current flow through the output between an alarming direction flowing from said first output node and a supervising direction flowing from said second output node;

    isolation means, having an input coupled in parallel with the switching means output between said first and second output nodes, and having an output for coupling with the common circuit, for allowing current in the alarming direction flowing from said first output node to flow into the common circuit and for blocking current flow between the interface circuit and the common circuit when current is flowing in the supervising direction from said second output node; and

    resistor means connected in parallel with the switching means output for providing a supervising current flow path in the interface circuit when current is flowing in the supervising direction;

    whereby the interface circuit is supervised for electrical faults regardless of current flow direction yet isolated from the common circuit and the other interface circuits when the current is not flowing in the alarming direction.

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