Locally nulled sine-wave total power alarm for intrusion detecti

Details Locally nulled sine-wave total power alarm for intrusion detecti Locally nulled sine-wave total power alarm for intrusion detecti

1988-06-16

1990-02-20

Griffin, Robert L.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

H04B 900

Patent

active

049033395

ABSTRACT:
An intrusion detection optical communication system modifies the original data signal to include a synchronizing periodic waveform. The receiver generates an inverted synchronizing periodic waveform signal corresponding with the transmitted signal to null the same under normal operation. When an intrusion in the optical system arises, power is extracted from the system and the nulled condition is disrupted. The disruption is detected and activates an alarm circuit when the disruption is above a threshold value.

REFERENCES:
patent: 4000416 (1976-12-01), Goell
patent: 4144530 (1979-03-01), Redfern
patent: 4207561 (1980-01-01), Steensma
patent: 4217488 (1980-08-01), Hubbard et al.
patent: 4399565 (1983-08-01), Jarret
patent: 4435850 (1984-03-01), Bowen et al.

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