A repeater on a hilltop or tall building can allow stations that are out of each other's line-of-sight range to communicate reliably. Without a repeater, these systems are limited in range by the curvature of the Earth and the blocking effect of terrain or high buildings.
Radio repeaters improve communication coverage in systems using frequencies that typically have line-of-sight propagation. Repeaters are found in professional, commercial, and government mobile radio systems and also in amateur radio. A repeater sited at a high elevation can allow two mobile stations, otherwise out of line-of-sight propagation range of each other, to communicate. A radio repeater(Two-way repeater or 2 way repeater) is a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances.
