Relays Relays are electronic or electromechanical switches that operate under the control of an external circuit. Originally when first invented in 1835, electromechanical relays consisted of an electromagnet and a set of contacts. When the electromagnet was energized, it closed the contact by attracting a lever held by a spring. When no current is flowing through the circuit, the electromagnet got demagnetized and the spring pulled back the lever and the circuit was left open. This type of Read more [...]