Abstract: The system of detecting motion by means of a video detector which consists in directing at least one television camera (20) into the surveillance area, and reproducing the image from the said camera on a television (25) screen, characterized in that the television screen display is divided into a matrix of elemental detection zones (15) positioned in a selected number of columnms (1 to 14) with each detection zone being a selected number of scan lines (0-8) high, processing the elemental detection zones in each column in a sequential manner by integrating (28) a first detection zone in the column and at the last scan line converting to digital format in an analogue-to-digital converter (29) and placing in a memory (49) and resetting the integrator to process the next elemental detection zone and so on and subsequently comparing scans with earlier corresponding scans to detect errors representing movement, further characterized by programmable window means generated by a rectangular window generator (51) to el