A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
A relay
An automotive-style miniature relay with the dust cover taken off
Simple electromechanical relay
Latching relay with permanent magnet
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow.
Electrical switches. Top, left to right: circuit breaker, mercury switch, wafer switch, DIP switch, surface mount switch, reed switch. Bottom, left to right: wall switch (U.S. style), miniature toggle switch, in‑line switch, push-button switch, rocker switch, microswitch.
Three push button switches (Tactile Switches). Major scale is inches.
A toggle switch in the "on" position
Triple-pole single-throw (TPST or 3PST) knife switch used to short the windings of a three‑phase wind turbine for braking purposes. Here the switch is shown in the open position.
