A cell phone repeater is a type of bi-directional amplifier which is used to boost the cell phone reception to the local area trough the usage of a small reception antenna. Modern cellular repeater amplifiers work by rebroadcasting cellular signals inside the building, warehouse, boats etc. Few models also allow multiple cell phones to use the same repeater at the same time. For more info visit powerfulsignal.com which provide varieties of such device for specific uses including system diagrams that will help in correct implementation.