The sensor terminal module relay is two or more electronic relays installed on a circuit board, and the input and output are led to the terminal through the circuit. Usually in place of the central relay. The relay module is composed of relays, relay sockets, light-emitting diodes, zener diodes, current limiting resistors, varistors, input and output terminals, PCB boards, and rail mounts.

When making an automated electrical control cabinet, a small central relay will be added to the PLC control load. Now industrial automation has been developed in the direction of integration, and then the sensor terminal relay module has been developed. PLC can directly control the coil of the relay module. The corner contacts of the relay module control the load. The advantage is that the size of the relay module is small, only 1/2 of the volume of the small central relay, and the contact current is larger than that of the small relay, generally 10A, 12A, 16A , 30A, with a varistor, when the relay is disconnected, the sparks that occur play the role of arc extinguishing and advance the life of the relay.