The T21104 photoelectric amplifier module is designed to amplify output from a photodetector to a level suitable for operating devices requiring DC voltage signal input. The output of the photodetector is taken as the input to the module. A Schmitt Trigger circuit within the module ensures positive switching of the output state to a completel y "ON" or completely "OFF" condition. An internal sensitivity pot is used to adjust the input threshold current at which the amplifier will trigger. To ensure output stability a small amount of hysteresis (approximatel y 0 .2 volts) is built into the circuitry. An indicator LED is provided to mon - itor amplifier state. It is ON when the photodetector is dark and OFF when photodetector is light. The module can be connected so that its output is energized when the photodetector is either LIGHT or DARK.