DTMF Tone Decoder
Encode and decode DTMF (Dual-Tone Multi-Frequency) telephone tones. Convert between numbers and frequency pairs.
About DTMF
DTMF (Dual-Tone Multi-Frequency) is the system used by touch-tone phones. Each key produces two simultaneous tones - one from a low frequency group (697-941 Hz) and one from a high frequency group (1209-1633 Hz).
What is DTMF?
DTMF (Dual-Tone Multi-Frequency) signaling is the system used by touch-tone telephones. When you press a key, the phone generates two simultaneous tones that identify the digit.
How DTMF Works
Each DTMF key combines one frequency from a low group (697, 770, 852, or 941 Hz) with one from a high group (1209, 1336, 1477, or 1633 Hz). This dual-tone approach makes the system robust against voice interference.
DTMF in Geocaching
DTMF puzzles in geocaching might present:
- Audio files: Recordings of touch-tone sequences
- Frequency pairs: Listed Hz values to decode
- Spectrograms: Visual representations of DTMF tones
- Phone number puzzles: Hidden coordinates in phone numbers
Extended DTMF (A, B, C, D)
The fourth column (1633 Hz) produces tones A, B, C, and D. These were originally for military use and are found on some specialized equipment. They occasionally appear in puzzles.
Decoding DTMF
To decode DTMF from audio:
- Use audio analysis software to identify frequency peaks
- Find the low frequency (697-941 Hz range)
- Find the high frequency (1209-1633 Hz range)
- Cross-reference in the DTMF matrix