Essentially, an electrical relay is a mechanical switch used in devices such as traffic signal controllers. Its primary function is to switch on or off. It can be powered by DC or AC. It is usually used to control circuits that carry less than 20 amps.

Relays are composed of an iron core that contains a movable, spring-loaded part called the armature. This is attracted to the magnetic field when the relay is energized. The armature also closes electrical contacts when the relay is de-energized.

Relays are made from many different materials. These materials are used to ensure that the contacts operate properly. Some relays use copper contacts, which have a high contact resistance. Other relays use silver nickel contacts, which have a fine grain structure. Silver nickel contacts help reduce the effects of pitting.

Relays use three different contact pinouts. A contact that is normally open is known as Form A contact, while a contact that is normally closed is called Form B contact.

An electrical relay can also have more than one pole. A single pole switch is normally denoted as SP, and a double pole switch is DP. Double pole switches allow two circuits to be switched simultaneously.

Electrical relays can be powered by DC or AC. Relays are often used in televisions and temperature controllers. They are also used in automatic stabilizers. They can be used to switch picture tube televisions, which require a high AC voltage.