Security system with radio frequency coupled remote sensors
US4462022A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 12, 1981 |
| Grant date | Jul 24, 1984 |
| Priority date | — |
| Expiry date | Nov 12, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B29/16
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A wireless security system in which a sensor for detecting a security violation is provided with a radio frequency transmitter adapted to excite the receiver of a control unit at a different location, the transmitter of the sensor radiating a signal responsive to the occurrence of a security violation. The sensor also having means to periodically excite the transmitter after the lapse of a period of time to indicate that the sensor is in proper working order, that period varying randomly. The control unit is provided with a memory and stores responses to the random signals, and at intervals long with respect to the random periods, samples the memory. The control unit responds to the absense of a stored response from the transmissions of the sensor. In a preferred construction, a plurality of sensors are employed with a single control unit, each of the sensors radiating a unique encoded signal. The control unit may thus determine by sampling which of the sensors has failed to radiate a signal received by the control unit during the sampling interval of the control unit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.