Supervisory circuit for parallel connected devices
US3936821A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 15, 1974 |
| Grant date | Feb 3, 1976 |
| Priority date | — |
| Expiry date | May 15, 1994 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B23/00
- WIPO fieldControl
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.