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This is a GPRS / GSM Arduino expansion board developed by DFRobot. The capabilities of GPRS, DTMF, TTS speech all in one shield, operating frequency is EGSM 900MHz/DCS 1800MHz and GSM850 MHz/PCS 1900MHz.
It also supports UCS2 encoding data and text data format directly which makes your robot could do TTS voice broadcast at any time. It supports DTMF, once the DTMF feature was enabled, press the keys during a call can be converted into character, and can be used for remote control.