A broadcast relay station, relay transmitter, broadcast translator (U.S.), rebroadcaster (Canada), or repeater (two-way radio) is a broadcast transmitter which relays or repeats the signal of another radio station or television station, usually to an area not covered by the signal of the originating station. They may serve, for example, to expand the broadcast range of a television or radio station beyond the primary signal's coverage area, or to improve service in a part of the main coverage area which receives a poor signal due to geographic constraints. They may (but are not usually) used to create a single-frequency network.