Processor
ARM ARM9E family and above with DSP extensions

Background
DTMF (Dual-Tone Multi-Frequency) is the most common signaling method used within the telephone network, and has now largely replaced loop disconnect ("pulse") dialing. DTMF works by employing pairs of tones to code the digits 0-9, #, * and A-D. DTMF are now also being used for callers to service centers to select desired services via telephones.