A device that receives signals in one circuit and automatically delivers corresponding signals to one or more other circuits. A repeater is most often used with telephonic or telegraph circuits or in radio systems, usually amplifying the signal, and in pulse telegraphy performs pulse regeneration on the transmitted pulses. Repeaters can operate either on signals in one direction only or on two-way signals; telephone repeaters operate on four-wire circuits or two-wire circuits. A terminal repeater is a repeater that is used at the end of a trunk feeder or transmission line.