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From Nordan Symposia
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==Origin==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], set of fresh hounds, from ''relayen''
*[http://en.wikipedia.org/wiki/17th_century 1651]
==Definitions==
*1a : a supply (as of horses) arranged beforehand for successive relief
:b : a number of [[persons]] who relieve others in some [[work]] <worked in relays around the clock>
*2a : a race between teams in which each team member successively covers a specified portion of the [[course]]
:b : one of the divisions of a relay
*3: an [[electromagnetic]] device for remote or [[automatic]] control that is actuated by variation in conditions of an electric [[circuit]] and that operates in turn other devices (as switches) in the same or a different circuit
*4: servomotor
*5: the [[act]] of passing along (as a [[message]] or ball) by [[stages]]; also : one of such stages
==Description==
A '''relay''' is an [[electrically]] operated switch. Many relays use an [[electromagnet]] to operate a switching [[mechanism]] mechanically, but other operating principles are also used. Relays are used where it is [[necessary]] to control a [[circuit]] by a low-power [[signal]] (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the [[signal]] coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early [[computers]] to perform [[logical]] operations.
A type of relay that can handle the high [[power]] required to directly [[control]] an electric motor or other loads is called a [http://en.wikipedia.org/wiki/Contactor contactor]. [http://en.wikipedia.org/wiki/Solid-state_relay Solid-state relays] control power [[circuits]] with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these [[functions]] are performed by digital instruments still called "[http://en.wikipedia.org/wiki/Protective_relay protective relays]".[http://en.wikipedia.org/wiki/Relay]
[[Category: Physics]]
==Origin==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], set of fresh hounds, from ''relayen''
*[http://en.wikipedia.org/wiki/17th_century 1651]
==Definitions==
*1a : a supply (as of horses) arranged beforehand for successive relief
:b : a number of [[persons]] who relieve others in some [[work]] <worked in relays around the clock>
*2a : a race between teams in which each team member successively covers a specified portion of the [[course]]
:b : one of the divisions of a relay
*3: an [[electromagnetic]] device for remote or [[automatic]] control that is actuated by variation in conditions of an electric [[circuit]] and that operates in turn other devices (as switches) in the same or a different circuit
*4: servomotor
*5: the [[act]] of passing along (as a [[message]] or ball) by [[stages]]; also : one of such stages
==Description==
A '''relay''' is an [[electrically]] operated switch. Many relays use an [[electromagnet]] to operate a switching [[mechanism]] mechanically, but other operating principles are also used. Relays are used where it is [[necessary]] to control a [[circuit]] by a low-power [[signal]] (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the [[signal]] coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early [[computers]] to perform [[logical]] operations.
A type of relay that can handle the high [[power]] required to directly [[control]] an electric motor or other loads is called a [http://en.wikipedia.org/wiki/Contactor contactor]. [http://en.wikipedia.org/wiki/Solid-state_relay Solid-state relays] control power [[circuits]] with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these [[functions]] are performed by digital instruments still called "[http://en.wikipedia.org/wiki/Protective_relay protective relays]".[http://en.wikipedia.org/wiki/Relay]
[[Category: Physics]]
