Optical positive feedback sensor circuit

Claim 1

A photoelectric apparatus for sensing recorded information expressed in the form of the presence or absence of indicia born on a moving carrier and for expressing such information as sensed in the form of an electric signal, comprising: a gallium arsenide light-emitting device positioned adjacent said carrier for illuminating said carrier such that the illumination is propagated by said carrier according to the presence and absence of said indicia; a phototransistor positioned adjacent said carrier for detecting said illumination from said diode as propagated by said carrier; a nonlinear amplifier connected to said phototransistor and said diode for amplifying the output of said diode and providing the system output of said apparatus, including a power supply, at least one nonlinear amplification stage, and means coupling said power supply to said diode for maintaining illumination from said diode during periods of otherwise insufficient amplifier output to maintain operation of said apparatus; and feedback means electrically connecting said amplifier to said diode for positively feeding back a portion of the output of said amplifier to said diode; such that when said phototransiStor detects said illumination the electrical circuit of said apparatus rapidly builds to saturation.