DTMF Tone Generator
The phone keypad's dual tones โ play, dial sequences, export WAV.
About this generator
A full 4ร4 keypad โ digits, * and #, plus the AโD column consumer phones never got โ that plays authentic dual tones, dials whole sequences with correct timing, and exports studio-clean WAV files for testing.
Why every phone key is a chord
Press 5 on any touch-tone phone and you hear 770 Hz and 1336 Hz simultaneously โ one frequency from the key's row, one from its column. The 1963 Bell Labs design is quietly brilliant: the eight frequencies were chosen so that no key's pair can be counterfeited by harmonics of another or by a human voice singing along, which made the signalling robust enough that it still runs the world's phone menus today โ every "press 2 for support" decodes these exact tones, six decades on. The mysterious AโD column is real DTMF too: military AUTOVON priority levels and ham-radio signalling, present in the spec, absent from your phone. Honest practical uses: feeding known-good tones to IVR systems under test, generating DTMF test fixtures for audio pipelines, checking whether a line's tone recognition works, and hearing your own number as the tiny melody it is. The WAV export writes precise frequencies at standard timing โ cleaner than any phone speaker. Single tones and the analyzer โ where each key shows as twin spikes โ complete the lab.
Frequently asked questions
What are the A, B, C and D keys?
Real DTMF from the original spec โ a fourth column used by military phone priority systems and ham radio. Consumer keypads dropped the column, but the tones remain standard.
Can these tones actually dial a phone?
Held up to an old landline's mouthpiece, genuinely yes โ that's how phone phreaking toys worked. Modern mobile networks signal digitally, so it's history you can hear rather than a bypass.
Why two frequencies per key?
Robustness: a single tone could be faked by noise, voice or harmonics. The dual-tone pairs were chosen so only a deliberate generator produces valid combinations โ which is why voice never accidentally dials.
What's the WAV export for?
Testing: IVR phone menus, tone-recognition code, audio pipelines. The file contains mathematically exact frequencies at standard timing โ a cleaner test signal than any recorded phone.