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A relay is defined as an electrical device, typically incorporating an electromagnet, that is activated by a current or signal in one circuit, to open or close another circuit.

Carl Gauss and Willhem  Weber developed an electromagnetic relay in 1833.  Although, Joseph Henry claimed he invented the relay in 1835.

Relays are simply switches that open and close circuits either electromechanically or electronically. Relays control an electrical circuit by opening and closing contacts in a circuit. A relay is used when something in a circuit needs to turn off and on.

Types of Relays

Protective Relays

Protective relays prevent equipment damage by detecting electrical abnormalities, overcurrent, undercurrent, overloads and reverse currents. Relays are commonly used to switch starting coils, heating elements, pilot lights and even audible alarms.

Electromechanical Relays

In electromechanical relays the contacts are opened or closed by a magnetic force.

Solid State Relays

In solid state relays there are no contacts and switching is strictly electronic.

Hybrid Relay

The hybrid relay uses both technologies from the electromagnetic relays and the solid state relay. It eliminates the disadvantages of both while providing extremely reliable switching.

Thermal Relay

Based on the effects of heat, with the rise in temperature from the limit, it directs the contacts to switch from one position to other. These are mainly used in motor protection and temperature sensors as well as control elements. The best examples of these relays are thermal overload relays.

Reed Relay

Reed Relays consist of magnetic strips that are sealed within a glass tube. This reed acts as an armature and a contact blade.  The magnetic field applied to the coil is wrapped around this tube that makes these reeds move so that the relay can switch.

It is important to consider the type of relay required based on an application’s electrical requirements, cost constraints and life expectancy.  At Global Electronic Services we stock hundreds of all types of relays.  Be sure to visit us online at or call us at 1-877-249-1701 to learn more about our services. We’re proud to offer Surplus, Complete Repair and Maintenance on all types of Industrial Electronics, Servo Motors, AC and DC Motors, Hydraulics and Pneumatics. Please subscribe to our YouTube page and Like Us on Facebook! Thank you!

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