GPRS / GSM Shield for Arduino Quad-Band 850/ 900/ 1800/ 1900 MHz GPRS multi-slot class 10/8 GPRS mobile station class B Compliant to GSM phase 2/2+ Class 4 (2 W @850/ 900 MHz) Class 1 (1 W @ 1800/1900MHz) Control via AT commands (GSM 07.07 ,07.05 and SIMCOM enhanced AT Commands)