1.gsm modem, rs485 modem 2.with standard TCP/IP protocol stack, i/o 3.Support transparent data transfer 4. Support DDNS IP modem, ... terminal,GPRS DTU, TCP/IP modem, Support transparent data transfe, gprs ip modem, gsm modemgprs modem with rs232 rs485 io for m2m meter ... real time operating system. It supports RS232 and RS485 (or RS422) port that can conveniently and transparently connect one device ...