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°c to +50°c • storage temperature range: -40°c to + 60°c • humidity: 5% to 95% ac-to-dc switching power supply • voltage: 100 - 300 v ac • frequency: 50/60 hz