Anti-fraud alarm transmission line security system

Details Anti-fraud alarm transmission line security system Anti-fraud alarm transmission line security system

1976-08-27

1978-01-24

Waring, Alvin H.

Communications: electrical

Audible indication

Pneumatic-type sound producer

340416, G08B 1900

Patent

active

040706699

ABSTRACT:
A transmitter transmits a continuous "non-alarm" signal to a monitoring center. When an alarm occurs, e.g. if a burglary takes place, the "non-alarm" signal ceases, and an alarm is indicated at the monitoring center. To prevent the "non-alarm" signal being pre-recorded and subsequently being relayed to the monitoring center to render the transmitter ineffective, the monitoring center transmits random trap pulses having a carrier frequency different from the "non-alarm" signal. If the monitoring center detects a trap pulse at any time other than when transmitting such a pulse, an alarm is indicated.

REFERENCES:
patent: 3307176 (1967-02-01), Sadler
patent: 3934237 (1976-01-01), Gysell et al.

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