Dual Band LTE Repeater also known as cell phone repeaters were developed to address the two factors that cause poor cell phone reception. They're designed to amplify a weak outside signal and bypass any obstructions to provide a strong inside signal to an area that was originally lacking.The system works by mounting an outside antenna in a location that currently has signal, which is typically on the roof. The signal is passed from the outside antenna, by a cable to a signal amplifier inside the building. Once the signal is amplified, it is then sent to an inside antenna, where it is broadcast out to the area which needs better reception. The system also works in reverse, with the signal from your phone being amplified and broadcast back to the tower, ensuring strong, two-way communication.