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relay1
n. /ree"lay/; v. /ree"lay, ri lay"/, n., v., relayed, relaying.n.1. a series of persons relieving one another or taking turns; shift.2. a fresh set of dogs or horses posted in readiness for use in a hunt, on a journey, etc.3. Sports.a. See relay race.b. a length or leg in a relay race.4. Mach. an automatic control device in which the settings of valves, switches, etc., are regulated by a powered element, as a motor, solenoid, or pneumatic mechanism actuated by a smaller, sensitive element.5. Elect. a device, usually consisting of an electromagnet and an armature, by which a change of current or voltage in one circuit is used to make or break a connection in another circuit or to affect the operation of other devices in the same or another circuit.6. (cap.) U.S. Aerospace. one of an early series of experimental low-altitude, active communications satellites.v.t.7. to carry forward by or as if by relays: to relay a message.8. to provide with or replace by fresh relays.9. Elect. to retransmit (a signal, message, etc.) by or as if by means of a telegraphic relay.v.i.10. Elect. to retransmit a signal or message electronically.[1375-1425; (v.) late ME relaien to unleash fresh hounds in a hunt < MF relaier, OF: to leave behind, RELEASE, equiv. to re- RE- + laier to leave, dial. var. of laissier < L laxare (see RELAX); (n.) late ME relai set of fresh hounds < MF, deriv. of relaier]relay2/ree lay"/, v.t., relaid, relaying.re-lay.
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in electricity, electromagnetic device for remote or automatic control of current in one (relay) circuit, using the variation in current in another (energizing) circuit. For example, in a solenoid (q.v.) the core will move when energized to open or close a switch or circuit breaker. Many relays are protective in function. Probably the earliest was the old telegraph relay, in which the energizing current moved an armature carrying a contact point to close a sounder circuit. Relays were important in early computer designs before they were replaced by the faster vacuum tubes and, later, by transistors. They are also used in railway (railroad) block signalling, the energized relay being de-energized by shorting through car axles. Currently in wide use are telephone relays. The illustration shows the essentials of a typical general-purpose relay.* * *
Universalium. 2010.
