In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. In communication, In popular understanding, a repeater also called a relay, can extend the communication distance. In the radio solution, relay is very common. It can double the communication distance of the handheld unit. It is mainly used to solve the distance problem in the communication of handheld walkie-talkies.