Signal relays have the advantages of fast operation, stable operation, long service life, and small size. Widely used in power protection, automation, motion, remote control, measurement and communications devices. Signal relays generally consist of iron cores, coils, armature, contact reeds, etc. As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil to generate an electromagnetic effect, and the armature will absorb the pulling force of the return spring to the core under the action of the electromagnetic force to attract the armature. The movable contact and the stationary contact (normally open contact) are attracted.

Signal relay can expand the control range. When the multi-contact relay control signal reaches a certain value, the multi-circuit can be switched, disconnected and connected at the same time according to the different forms of the contact group. With a very small amount of control, it is possible to control large power circuits. When multiple control signals are input to the multi-winding relay according to the specified form, after comparison and synthesis, a predetermined control effect is achieved. The relay on the automatic device together with other electrical appliances can form a program control circuit to realize automatic operation.