1 An electrical switch that allows a low power to control a higher one. A small current energizes the relay, which closes a gate, allowing a large current to flow through.
2. An electromechanical or solid-state device operated by variations in the input which, in turn, operate or control other devices connected to the output.

They are used in a wide variety of applications throughout industry; such as, in telephone exchanges, digital computers, motor and sequencing controls, and automation systems.

Highly sophisticated relays are utilized to protect electric power systems against trouble and power blackouts; as well as, to regulate and to control the generation and distribution of electrical power.

In private residences, relays are used in refrigerators, automatic washers, dishwashers, and heat and air-conditioning controls.

3. An electromechanical switch operated by a flow of electricity in one circuit and controlling the flow of electricity in another circuit.

A relay composed essentially of an electromagnet with a soft iron bar, called an armature, held close to it.

A movable contact is connected to the armature in such a way that the contact is held in its normal position by a spring and when the electromagnet is energized, it exerts a force on the armature that overcomes the pull of the spring and moves the contact so as to either complete or to break a circuit.

A relay that remains in the "on" condition after actuation until reset by applying an independent electric input.

A relay is an electrical device such that electric current flowing through it in one circuit can switch on and off a current in a second circuit

1. A switch that opens and closes contacts by the action of an electromagnetic element.
2. A relay in which current flow through a coil produces a magnetic field that results in contact actuation.
3. A device that opens or closes contacts by settling "moving" contacts against "fixed" contacts when current passes through an electromagnet.

The electric current sets up a magnetic attraction between the core of the electromagnet and a hinged arm to the tip of which is attached the "moving" contact.

The movement of the arm towards the core of the electromagnet brings "moving" and "fixed" contacts together.

When an electric current is withdrawn, a spring returns the arm to to its original position and the contacts separate.

1. A device consisting of a coil and an armature that moves under the influence of a magnetic field produced by the coil to close or to open a contacting switch.
2. A protective relay operating on the principle of electromagnetic attraction; such as, a plunger relay or of electromagnetic induction.

An electronic circuit which provides the function of a relay (electromechanical switch operated by a flow of electricity in one circuit and controlling the flow of electricity in another circuit) but which has no moving parts.

A solid-state relay (an on/off control device) which uses no moving parts is one example of an electronic relay.

A relay which employs electronic tubes as components.

1. A relay in which two or more conductors which are separated by insulating material move because of the mutual attraction or by repulsion that is produced by electric charges applied to the conductors.
2. A relay whose actuator element consists of non-conducting media separating two or more conductors which change their relative positions because of the mutual attraction or repulsion of electric charges applied to the conductors.

A relay the operation of which is produced by an electrostrictive-dielectric actuator.

A relay that functions at a predetermined value of voltage.