Features:  Siemens module embedded  LCD display, Caller ID  Built in li-battery  Trunk port of PBX access  Redial, call divert , call waiting, call conference support  Hand-Free support  Call records  Incoming call reminder  GPRS Specifications: Air Interface Standard ?GSM 850/1800/1900 Phase 2+ Transmit Power ?GSM 850: 2 watts ?GSM 1800/1900: 1 watt Frequency Ranges Transmit Receive ?GSM 900 890-915 MHz 935-960 MHz ?GSM 1800 1710-1785 MHz 1805-1880 MHz . GSM1900 1850-1910Mhz 1930-1990Mhz Backup Battery: lithium battery Talking Time: up to 3 hours (network depended) Standard Time: up to 36 hours (network depended) Environment ?Operating temperature range: -10癈 to +50癈 ?Storage temperature range: -40癈 to + 60癈 ?Humidity: 5% to 95% AC-to-DC Switching Power Supply ?Voltage: 100 - 300 V AC ?Frequency: 50/60 Hz