Three terminal bidirectional thyristor, or AC transistor, is a semiconductor device widely used in power control and switching applications. It has applications in switch, phase control, chopper design, brightness control of lamps, speed control of fans, motors, and other aspects. The power control system aims to control the distribution level of AC or DC. This power control system can be used to manually or switch the power supply of electrical appliances when the temperature or light level exceeds a preset level.