Feedback control circuit for photosensors in magnetic tape drives

摘要

A magnetic tape recording and reproducing system in which a light reflective marker is on each reel of tape and has a feedback circuit connected between the light sensor and the source of light for controlling the intensity of the source to maintain the output substantially constant, notwithstanding changes of reflectivity of the tape or gradual changes of efficiency of the source of light. The feedback circuit provides improved detection of the passage of the reflective marker past the sensor.