DTMF decodes and encodes DTMF (Dual-tone multi-frequency) tones trough the phones speaker and microphone. Encoder: Always 2 tones are assigned to each key. The length of the tone and the pause between the tones can be set from 35ms to 1500ms. A total of 36 marco's can be used to play phone numbers, ham radio auto patch numbers, amateur radio echolink id's any many more.