The so-called relay is composed of ① electromagnetic magnet ② contact structure, "when the electromagnetic stone through a value above the current will produce electromagnetic attraction, the use of this electromagnetic attraction, can drive the contact structure work, the use of additional voltage and current on the coil (input signal) to control the mechanical contact opening and closing."

 

 

In a nutshell

 

Electrical signals are received through switches and transmitted to motors and other output relay devices