Repeater

In telegraphy an instrument for repeating the signals through a second line. It is virtually a relay which is operated by the sender, and which in turn operates the rest of the main line, being situated itself at about the middle point of the distance covered. In the simpler forms of repeater two relays are used, one for transmi ion in one direction the other for transmi ion in the other. An attendant switches one or the other in as required. Thus a common relay is virtually a repeater for its local circuit. If such a relay is placed half way down a line, and if the line beyond it is connected as its local, it becomes a repeater. Some forms of repeaters are automatic, and repeat both ways without the need of an attendant. It is the practice to somewhat prolong the signals sent through a repeater.