What is relay?

What is relay?

A relay is an electrical  control device that is an electrical device that causes a predetermined  step change in the controlled electrical quantity in an electrical  output circuit when the change in the input quantity (driver amount)  reaches a specified requirement. It has an interactive  relationship between the control system (also known as the input loop)  and the controlled system (also known as the output loop). Usually  used in automated control circuits, it is actually an "automatic  switch" that uses small currents to control high-current operation. Therefore, it plays a role in the circuit such as automatic adjustment, safety protection, and conversion circuit.