... : DTU, Modem, SMS Modem. These three working modes are optional. When set to Modem, single standard AT command (GSM07.05 and ... 07.07). When SMS Modem, user can set the message transmission ... 1 (1W) at DCS1800MHz and PCS1900MHzCompatible standardAT command(GSM07.05 and 07.07)Basic functionextend command, SMS, USSD, CSD, Embed TCP/IP Protocol ...