... 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 ... ohm, lighting protection(optional)SIM/UIMStandard 3V/1.8V user card interface, 15KV ESD protectionPowerTerminal block interface, reverse-voltage and overvoltage ...