Nextivity Cel-Fi RS2 Cell Phone Signal Booster for T-Mobile Only Improved Voice Coverage: Enables clear and reliable 3G voice connections within the coverage area - usually up to 1235 m2 (13,000 Sq. Ft.). Ease of Installation: Cel-Fi is a true &quot;Plug and Play&quot; system that doesn&#39;t require the installation of external antennas, bulky coaxial cables or a configuration set-up by the subscriber. Improved Data Throughput: For indoor areas with poor reception, Cel-Fi offers significant data throughput improvements - often in excess of four times the current rate! Improved Battery Life: Cel-Fi manages the power levels between the cell tower and user devices so that subscriber devices enjoy significant improvements in battery life ONLY compatible with T-mobile service. Will not work with any other cellular service, not compatible with Sprint, nor Verizon, nor AT&T