Two phone no. to access both GSM and PSTN. Auto detecting PSTN. Switch to GSM automatically when PSTN is not detected. Restricting calls to choose GSM or PSTN. Support call barring. Specilized SIM card in case of misuse in mobile phones after decrypt. Phone book storing up to 100 pieces of numbers. Support barring of incoming and dialed calls and speed dialing. Attached small keyboard to input more conveniently. 5 seconds prompt to switch to another call by pressing switch key during a talk, without disconnecting the original one. Support both PSTN and GSM virtual network function. Auto detect PSTN or GSM fault to dial the phone through proper network. 128*64 LCD with background light showing five lines of calling information, date and time. Support remote network management. Support carrier locking. Support keyboard locking. User can set up to 10 barred calls. Prefix IP no. ahead of long distance call automatically. GSM900/DCS1800MHz dual mode adaptation. Receiving and sending short messages. Calls records. Friendly interface using both text and images. Incoming caller ID for both GSM and PSTN. Intelligent power management. Detecting the batteries to recharge or discharge automatically. Displaying battery level and signal strength. 18 types of chord rings Internal or external antenna Low power design by providing backup batteries. Using industrial wireless module. 850/1900mHZ frequency optional.