Relay is a kind of electric switch. However, this switch is not directly by hand to control, but by foreign electrical signals to control, these foreign electrical signals or by all kinds of sensor produced, or by various programming software according to the instruction or program to be automatic obtained. So, the relay will be in accordance with the arrangement, automatically switching circuit, make all kinds of electrical equipment, appliances automatic control of electrical switch.
Relay is a kind of automatic electric appliance, which is widely used in electric power protection, production process automation and all kinds of automatic, remote, remote control, remote sensing and communication automation equipment, is one of the most basic electrical components in the modern automation system.
Relay is a kind of automatically intermittent control element. When the input quantity (or incentive quantity) meet certain prescribed conditions,it can be in one or more of the electrical output circuits produce scheduled jump a device.