re·lay1 • n. / ˈrēˌlā/ 1. a group of people or animals engaged in a task or activity for a fixed period of time and then replaced by a similar group: the wagons were pulled by relays of horses gangs of workers were sent in relays. ∎ [usu. as adj.] a race between teams usually of sprinters or swimmers, each team member in turn covering part of the total distance: a 550-meter relay race. 2. an electrical device, typically incorporating an electromagnet, that is activated by a current or signal in one circuit to open or close another circuit. 3. a device to receive, reinforce, and retransmit a broadcast or program. ∎ a message or program transmitted by such a device: a relay of a performance live from the concert hall. • v. / riˈlā; ˈrēˌlā/ [tr.] receive and pass on (information or a message): she intended to relay everything she had learned. ∎ broadcast (something) by passing signals received from elsewhere through a transmitting station: the speech was relayed live from the White House.
1. In networking, a means of passing information between two or more networks, each offering a similar network function but each using a different protocol. In general a relay differs from a gateway or bridge in offering a store-and-forward service rather than a real-time service. As an example, a mail relay may be used to pass mail messages between networks using different mail protocols. See also cell relay, frame relay.
The term relay is used in some communities as synonymous with bridge or gateway. These three terms have meanings that vary between different communities at the same time, and within a given community at different times.
2. An electrically controlled switch enabling small signals to control much larger powers than would normally be possible as well as providing isolation between circuits. Various contact arrangements, e.g. normally open, normally closed, change-over and multiple poles, are available, as are bistable versions.