Title: Supervisory circuit for parallel connected devices

Abstract: A supervisory circuit for a plurality of continuously-conductive alarm devices connected in parallel between a pair of conductors monitors the operability of the circuit as well as the operability of each of the devices. Alarm devices having a low impedance are connected between the conductors over a parallel-connected resistor and diode which unidirectionally increases the impedance of such devices. The alarm circuit is connected in one arm of a balanced bridge circuit which has a detecting circuit connected in a further branch of the bridge circuit for monitoring the impedance of the circuit and for providing a supervision signal in response to a change in the impedance of the alarm circuit indicating inoperability of a device or open or short circuit conditions for the conductors which connect the devices into the circuit.

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Inventors: Cooper, Glenn F. (West Springfield, MA, US)
Marceau, Daniel J. (Springfield, MA, US)

Application Number: 470063
Filing Date: 1974-05-15
Publication_date: 1976-02-03
Assignee: Standard Electric Time Corporation (Springfield, MA)
Primary Class(es): 340/510 340/513, 340/691.8
Other Classes:
US Patent Ref:

3389390	Jun, 1968	Waller	340/285.
3544984	Dec, 1970	Hanson	340/233.

Other Refs:
Primary Examiner: Pitts, Harold I.
Assistant Examiner:
Attorney: Johnson, Dienner, Emrich & Wagner