Internal antenna booster works to capture and emit a stronger signal Placing electronic device behind cell phone's fixed antenna increases the surface area Electronic booster enhances signals, resulting in fewer dropped calls How Does it Work? The ultra-thin Internal Antenna Booster works like a dish on a satellite to capture and emit a stronger signal. Mount the Cell Phone Antenna Booster internally under battery or externally to your cell phone. By placing the internal antenna behind the fixed antenna of the phone or attaching it to the back of your phone, you increase the surface area for sending and receiving messages. This Antenna is a passive device designed to pick up weak RF signals from the cell tower, and re-radiate that signal to the phones built in antenna and improve the phone's performance. Works with nearly ALL Cell Phones: Works with ALL cell phones including digital, analog and tri-band phones. Works on 900MHz, 1800MHz and 1900MHz range systems (except the Nextel 500 & 800 series due to screw-in batteries). AT&T, Bravo, Nokia, Motorola, Samsung, Phillips, Sony, LG, NEC, Sprint, Sanyo, Ericsson, OKI Phones, Qualcomm, Startac, TimePort, Mitsubitshi, LG, Jazz, AudioVox, Kyocera, WorldLine, Fido plus many other brands.