... protocol stack, i/o 3.Support transparent data transfer 4. Support DDNS IP modem, RS232 modem, GSM IP modem, GPRS data modem, data terminal,GPRS ... DTU, TCP/IP modem, Support transparent data transfe, gprs ip modem, gsm modemgprs ... DDNS) and IP access to data centerDesign with standard TCP/IP protocol stackSupport APN/VPDNProduct Specification Cellular ...