KuWFi Mini GSM 900mhz Mobile Cell Phone Signal Booster Amplifier Cellphone Signal Repeater, Mobile GSM900 Repeater Amplifier to Expand Mobile Phone Signal (Including Antenna) Frequency range: Uplink 890 ~ 915MHz Downlink 935 ~ 960MHz Gain (dB): Uplink Gp55 Downlink Gp60 Cell phone signal amplifier is designed to solve the blind signal designed for mobile phone products. As the mobile phone signal is transmitted by electromagnetic waves to establish a communications link, the building of the barrier, in some tall buildings inside the basement of some places such as malls, restaurants, places of entertainment such as karaoke OK sauna and massage