DTMF the row and columns DTMF DTMF (Dual-tone multi-frequency) DTMF DTMF DTMF DTMF DTMF DTMF DTMF DTMF tones DTMF DTMF Dual-tone multi frequency signaling (DTMF) DTMF DTMF DTMF DTMF DTMF DTMF DTMF tones