The use of relay is widely. Those who need to circuit switching place can use relay. Or all kinds of switch can be used instead of relay to become automatic switch.
Relay is everywhere in modern society. Such as household appliances in various temperature control, all kinds of remote control device; In the car starting control, light, door, window, wipers, turn light, air conditioning automatic control; Uninterrupted power supply automatic switching, street lamp automatic open and shut; The traffic signal lamp automatic switching, telephone switchboard automatic connection; Network monitoring, industrial automation process control and so on is inseparable from the relay. Modern weapons and equipment and the use of relay, because modern weapons and equipment are automation or the remote control. Aerospace equipments are more from relay, because they can work only on automatic control and remote control.