GB946375A - Building protection system - Google Patents

Abstract

946,375. Electric selective signalling systems; burglar alarms. RAD-O-LITE Inc. Aug. 22,1962, No. 32233/62. Headings G4H and G4N. The lights in a building (e.g. shop or factory) can be turned on from a remote point, (e.g. a patrolling police car) by means of an audio frequency signal modulated on a r.f. carrier, and, if desired, the receiver in the building can be linked to a burglar alarm system so that in the event of an alarm being given the lights in the building are also turned on. Transmitter. The transmitter comprises a crystal controlled r.f. oscillator 1, Fig. 1, modulated by the output of a 115 c/s audio frequency oscillator 33, 28, and feeding a tuned aerial 6, 7. A switch 19 permits the carrier frequency to be changed so that other equipment may also be controlled. A modified transmitter, suitable for use by a night watchman (Fig. 5, not shown) is described using a neon oscillator for the audio frequency signal. Receiver (Fig 2). The receiver in the building includes a thyratron 57, Fig. 2, which controls a relay which in turn controls the lights, the thyratron being so biased, via a resistor 59 (the points A and B being normally joined by a very low impedance) that it only conducts in the presence of a received audio frequency modified signal. The thyratron is also coupled to the A. C. mains supply which effects its resetting. Burglar alarm. The receiver in the building is such that if the bias on the thyratron is removed the thyratron will conduct. Thus by arranging that the connection between points A and B is broken by a burglar it follows that the lights will be turned on when a burglar is detected.