Surveillance zone monitor - compares successive zone rages to detect movement in zone

摘要

The surveillance appts. uses a matrix of photosensitive elements (2) to form a charged image of the zone under surveillance. An electrical signal representing the image is applied both directly and through a delay circuit (6) to a comparison circuit (3) which thus compares two time-spaced images of the surveillance zone. Any difference in the images arising from movement within the zone is detected by the comparison and appears as a signal at the output of the comparison circuit (3).