The Phonetone cell signal booster boosts signal for multiple cellular devices and users, so you can experience strong signal in your home, office, basement or metal building. The users within the coverage of the cell phone signal booster will enjoy fewer dropped calls, better voice quality, faster data speeds and smoother streaming video on band 12/17 and band 13. The booster works for the two largest cell carries in the USA - Verizon and AT&T. It is approved to operate on frequency bands 12, band 17 and 13 without interrupting or harming any cell carriers' signals to and from the cell tower Frequency Range: Band 12/17: Uplink 698-716MHz; Downlink 728-746MHz Band 13: Uplink 776-787MHz; Downlink 746-757MHz Note: 1. The booster can only amplify signal, it can't create signal. If there is no signal outside or the outside signal is too weak, the booster can't work. You had better have 1-2 bars of signal outside to use the booster. 2. The booster can only works well when the frequency band of your phone is the same with that of the booster, please check the frequency band of your phone before purchase.