1.gsm modem, rs485 modem 2.with standard TCP/IP protocol stack, ... i/o 3.Support transparent data transfer 4. Support DDNS IP modem, RS232 modem, GSM ... transparent data transfe, gprs ip modem, gsm modemgprs modem with rs232 rs485 io for m2m meter readinggprs ... DDNS) and IP access to data centerDesign with standard TCP/IP protocol stackSupport APN/VPDNProduct ...