TV camera alarm detection unit - has threshold detectors responding to changes in illumination caused by intruder

摘要

Switching circuitry coupled to a t.v. camera uses a change in illumination to detect the presence of an intruder. The video signal output of the camera, that has a fundamental frequency of 50 H2, is transmitted to an amplifier (A) with a bandpass characteristic of 0.16 to 16 H2. A threshold trigger (B) shapes the signal into a pulse of defined period. - A parallel channel has a peak value detector (C) that triggers a shaper (D) and a video signal control stage (G) provides a further output. All three signals are coupled to detection logic. If an intruder enters the field the alarm is triggered.