DTMF Dual-tone, multi-frequency Dual-tone, multi-frequency DTMF DTMF (Dual-tone multi-frequency) DTMF DTMF (Dual-tone multi-frequency) the row and columns https://en.wikipedia.org/wiki/Dtmf the row and columns Dual-tone, multi-frequency Dual-tone, multi-frequency DTMF DTMF DTMF Standard DTMF https://en.wikipedia.org/wiki/Dtmf DTMF DTMF http://en.wikipedia.org/wiki/Dtmf Dual-tone, multi-frequency DTMF DTMF the row and columns DTMF DTMF DTMF DTMF