초록 ▼

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 violati

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.

대표청구항 ▼

A supervised wireless security system comprising a sensor including a radio frequency transmitter adapted to be located at an area to be secured, and a control unit located at a distance from the sensor including a radio frequency receiver, characterized by the improved construction wherein the sens

A supervised wireless security system comprising a sensor including a radio frequency transmitter adapted to be located at an area to be secured, and a control unit located at a distance from the sensor including a radio frequency receiver, characterized by the improved construction wherein the sensor includes repetitive means for actuating the radio frequency transmitter after the lapse of a first period of time, the duration of said first period of time varying randomly, said means of exciting the radio frequency transmitter deactuating the transmitter after the lapse of a second period of time short compared to the first period of time, and the control unit includes a random access memory coupled to the receiver for receiving and storing signals from the transmitter, said control unit also including means for sampling the memory at intervals to determine the existence of a response to a signal from the transmitter, the sampling intervals of the control unit being long compared to the first period of time.