Cell phone becomes especially helpful when people get into critical situations. In case of emergency a timely call can save somebody’s life. Unfortunately, there are still some places where they can find themselves “out of coverage” No signal at all... Usually those places are either too far from the cell phone base station or located inside underground constructions, how does it works : The outside antenna catches low signal from operator servicer’s base station and delivers it to cell phone repeater through the connection cable (coax). After the signal is accepted by the mobile repeater, this device amplifies it. (coax) to the inside antenna. Then this amplified signal goes through the connection cable and after that, the amplified signal transmits to your cell phone. Finally, your cell phone will get good signal, never on and off.