The design of SW03A adopts a small power extended solid-state relay to drive three single-phase or three-phase high-power reverse parallel thyristors or bidirectional thyristors. Input level and temperature control instrument duty cycle (S-type, SSR) regulation output type instruments are compatible. It is installed using DIN standard rails or four hole screws. The input uses UL standard power wiring terminals, and the output uses pluggable terminals, making it convenient for users to use. Both 220V AC and 380V AC can work. The factory operates in a three-phase mode with J1 and J2 short circuits, and only the L1 LED is retained as the input indicator. J1 and J2 open circuits are three independent single-phase.