Engineering Dictionary of Electronic Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

"R" to "Rad", "Rai" to "Rea", "Rec" to "Relat",
"Relay" to "Resol", "Reson" to "Rh", "Ri" to "Rm", "Ro" to "Rz"

Relays are depicted just like mechanical switches on schematics. However because of interconnection, the switch portion of the relay may not be shown with the coil portion of the relay.
SPST; Single Pole Single Throw
SPDT; Single Pole Double Throw
DPST; Double Pole Single Throw
DPDT; Double Pole Double Throw
Solid State relays would appear the same on a schematic; however the coil portion of the relay would be replaced by some other component symbol, depending on the element used within the device.

Relay Schematic Switch Symbols
Relay Schematic Symbols

Relay. An electromagnetic device with one or more sets of contacts that change position by the magnetic attraction of a coil to an armature. Related; Relay Manufacturers. A relay is a low-powered device used to activate a high-powered device.

Picture of Mechanical Relay, Plastic see-through case
Relay Schematic
Relay Schematic

An electromechanical or semiconductor switch (i.e., solid-state relay) in which a current or voltage applied across one port or terminal controls electrical currents or voltages that appear across another terminal or terminals.

Relay Driver. An integrated circuit designed to handle the large load of a relay. An IC that can sink a heaver than normal amount of current and drive a high voltage. A 7409 Open Collector IC drives a low current medium voltage relay coil. A Peripheral Driver is a class of ICs that could be used to drive relays.

Open Collector Relay Driver Schematic
Relay Drive IC

In some cases ICs are specifically designed to drive high inductive loads, or relays. The coil of a relay is an inductive load. The IC below contains back-to-back Zener diodes to protect against both positive and negative voltage transients across the FET and clamp the output voltage.

Relay Driver, Internal IC Schematic
Relay Driver IC Schematic

The input Zener diodes protect the input of the IC against ESD [Electrostatic Discharge] and have nothing to do with relay operation.

Relay Contact Styles
PC motherboard

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