The GSM RF Repeater is designed to solve problems of weak mobile signal, which is much cheaper than adding a new base station (BS). Main operation of this repeater is to receive low-power signal from BS via radio frequency (RF) transmission and then transmit the amplified signal to the areas where network coverage is inadequate. And the mobile signal is also amplified and transmitted to the BS via the opposite direction. According to your requirement for working frequency, you can choose either type of our GSM RF repeaters: Band Selective RF Repeater: to amplify all signals in the whole band (bandwidth is customized) Channel Selective RF Repeater: to amplify only the signals transmitted by the customized 1 (2 or 4) channel (a narrow band with customized central frequency)