1,fast sending sms 2,RS232 & USB & RJ45 3,800/850/900/1800Mhz 4,software support ... SIM cards, simultaneously to send text messages. Key Features♦USB/RS232 GSM modem pool♦Based on Wavecom industrial modules Q24plus,Q2406 ... . serial port gsm modem serial port gsm modem GSM modem/rs232 16 port gsm modem pool to send bulk sms serial ...