relay

n. [ F. relais (cf. OF. relais relaxation, discontinuance, It. rilascio release, relief, rilasso relay), fr. OF. relaissier to abandon, release, fr. L. relaxare. See Relax. ] 1. A supply of anything arranged beforehand for affording relief from time to time, or at successive stages; provision for successive relief. Specifically: (a) A supply of horses placced at stations to be in readiness to relieve others, so that a trveler may proceed without delay. (b) A supply of hunting dogs or horses kept in readiness at certain places to relive the tired dogs or horses, and to continue the pursuit of the game if it comes that way. (c) A number of men who relieve others in carrying on some work. [ 1913 Webster ]

2. (Elec.) In various forms of telegraphic apparatus, a magnet which receives the circuit current, and is caused by it to bring into into action the power of a local battery for performing the work of making the record; also, a similar device by which the current in one circuit is made to open or close another circuit in which a current is passing. [ 1913 Webster ]

Relay battery (Elec.), the local battery which is brought into use by the action of the relay magnet, or relay. [ 1913 Webster ]

a. (Mach.) Relating to, or having the characteristics of, an auxiliary apparatus put into action by a feeble force but itself capable of exerting greater force, used to control a comparatively powerful machine or appliance. [ Webster 1913 Suppl. ]

. In a variable expansion central-valve engine, a small auxiliary engine for automatically adjusting the steam distribution to the load on the main engine. [ Webster 1913 Suppl. ]