Vktech&reg; CDMA PCS 850/1900MHz Dual Band Cell Phone Signal Booster Amplifier Repeater Please make sure distance above 10M between indoor and outdoor antenna, its better divides one from another by a wall. Please try to choose a good signal place to set up the outdoor antenna. Please sure that there are good signal 4-5 bars on your outdoor, or it will not work on your room. It could only strengthen cell phone signal, it could not produce cell phone signal,if there is no cell phone signal at all in your area, there is no need to use it. It works with worldwide GSM/EGSM 900MHz and DCS 1800MHz Networks, This device is strong to boost multiple users with maximum power, is cost effective solution with weak outside signal.