Features: GSM/PSTN Access Support(option) GPRS Function(option) PSTN Pass-through Support when Power Down Network Management Support GSM/GPRS data function(option) Modem mode (Access the Internet by GPRS through the PC serial port) Intelligent Call Routing Call ID Function Support Reverse Polarity Signal Output Time, Date, Local area, IP Function Saves 30 incoming call number, call lost number and call out number. Specifications: 1) Networks support: GSM 900 / 1800, 2) Operating temperature: 0% - 55% 3) Voltage: DC 5V 4) Backup battery: lithium battery 3.7V,1100mAh 5) Compatible with Nokia 3310 /3330 6) Adapter voltage: AC 50Hz+1%, 220V+10% 7) Stand-by time: 48 hours 8) Talk time: 2- 6 hours 9) Charging time: 6 hours