Relay

Relays

A relay is an electromagnetically operated switch. It was invented in the 19th century to make electric telegraph signals go farther. Nowadays relays control circuits with low-voltages. Many machines use them, including vehicles and electronics.

Relay Media

Electromechanical relay principle
Circuit symbols of relays (C denotes the common terminal in SPDT and DPDT types.)
Latching relay with permanent magnet
A mercury-wetted reed relay
Solid-state relays have no moving parts.
25 A and 40 A solid state contactors
Part of a relay interlocking using UK Q-style miniature plug-in relays

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