Abstract: The present invention comprises a low gain amplification circuit for amplifying the output of a light detecting transistor and producing a logic outputstrong enough to drive standard transistor logic circuitry. One or more bipolar non-symmetrical transistors are arranged in a cascade connected circuit to produce an amplification gain less than that of a single conventional transistor. The bipolar non-symmetrical transistors are reverse connected between the high level and low levels of the power supply and all feedback lines are eliminated while the frequency response is substantially increased.

Abstract: A light emitting source and a light sensing device are permanently fixed on one side of a moving object substantially separated one from the other. The light rays from the source are bent or reflected in a predetermined path so that the light rays to be sensed passes through at least two holes in said moving object before being sensed, thus enhancing the light to dark ratio and reducing the probability of false readings.

Abstract: Apparatus for sensing marks on a moving paper object includes light source means for transmitting light through a portion of a partially opaque mark and into the translucent fibers of a paper object. Light detecting means are provided for sensing the relative amount of light transmitted into said fibers by detecting the light in said fibers under said mark at an area transversely disposed from the portion of the mark where the light was applied.