By using a low-cost RS-170 camera and this circuit, a voltage that trades the position of an object in
the field of view of a camera is generated. IC2A and IC2B form a valid video gate that holds IC3 in reset during the internal vertical blanking to prevent false interpretation of the UBI as black video. IC4 is a black level detector. The circuit tests for a black object in the middle of each video line. IC5 latches the comparator"s output and produces a square wave whose duty cycle depends on where the black level is detected in the video field. Rl, CI, and IC6 integrate and buffer the analog output voltage.