This document describes the features and characteristics of the single-beam direct-ir infrared photodetector ST1100, including its limit parameters and photoelectric characteristics. The sensor is composed of a high-power infrared photodiode and a high-sensitivity photosensitive crystal. It has a slit width of 1mm and a light axis center of 2.5mm. The limit parameters include forward current, reverse voltage, input dissipation power, collector-emitter voltage, emitter-collector voltage, and output collector power consumption. The photoelectric characteristics include forward voltage drop, input reverse current, collector dark current, collector light current, output saturation voltage drop, transmission characteristics, and response time.