Phone keypad tones
Press and hold a key to play its two-tone signal, or type a number below to dial a sequence. Lower the device volume first.
Hold a key to hear it. Click or Tab into the keypad to use keyboard keys 0-9, *, # and A-D.
Accepts 0-9, *, # and A-D. Spaces and dashes are ignored. Up to 64 keys.
Ready. Audio starts only when you press a key or Play.
Each key is two sine tones added together at a modest level. Playback is local: no microphone, no upload, no network. Stop for discomfort or distortion.
Quick answer: turn the volume down, press and hold a key to hear its DTMF tone, or type a number and press Play sequence. Each key is the sum of two sine waves, one from a low group of four frequencies (697, 770, 852 and 941 Hz) and one from a high group of four (1209, 1336, 1477 and 1633 Hz). Everything runs in your browser; nothing is uploaded and no microphone is used.
What DTMF tones are
DTMF stands for dual-tone multi-frequency signalling. When you press a key on a push-button telephone, the phone sends two tones at once. One tone identifies the key's row on the keypad and the other identifies its column. Because the receiver listens for exactly one tone from each group, a pair is much harder to confuse with speech or background noise than a single tone would be.
The scheme was developed by the Bell System and sold as Touch-Tone dialling, replacing the pulses of rotary dials. The frequencies and tolerances are standardised internationally; the ITU-T publishes them in Recommendation Q.23, linked in the sources below. The tones are sometimes called touch tones, keypad tones or DTMF signals, and they all mean the same thing.
DTMF frequency table
The table below lists every key. Find the key's row for its low tone and its column for its high tone. For example, key 5 sits in the 770 Hz row and the 1336 Hz column, so it plays 770 Hz plus 1336 Hz.
| Low tone (row) | 1209 Hz | 1336 Hz | 1477 Hz | 1633 Hz |
|---|---|---|---|---|
| 697 Hz | 1 | 2 | 3 | A |
| 770 Hz | 4 | 5 | 6 | B |
| 852 Hz | 7 | 8 | 9 | C |
| 941 Hz | * | 0 | # | D |
How to use this generator
- Lower the device volume before you start. Two tones add together, so a key can sound louder than a single-tone test at the same setting.
- Press and hold a key with a mouse, finger or keyboard. The tone plays while the key is held, for at least about 100 ms so a quick tap is still audible. The readout shows the key and its two frequencies, such as "5 = 770 Hz + 1336 Hz".
- Keyboard shortcuts work only while the keypad has focus: click it or press Tab to move into it, then use the physical keys 0-9, *, # and A-D to play tones without the mouse. Typing inside the sequence box does not trigger tones.
- Press Download WAV to save the typed sequence as an audio file with your tone and gap lengths, which is useful for testing decoders offline.
- To dial a number, type it in the sequence box. Spaces and dashes are ignored. Set the tone length (40-500 ms, default 100) and the gap between tones (40-500 ms, default 100), then press Play sequence. Press Stop to end it early.
If nothing plays, browsers only start audio after a tap or key press, and some keep it suspended until then. Tap a key again, check that the device is not muted and that the right output is selected. The tool reports when the browser would not start audio instead of failing silently.
What a DTMF generator is useful for
- Testing phone menus and decoders. Developers can play known keys at a DTMF decoder, an interactive voice response (IVR) menu or a test harness and check what it recognises, including with different tone and gap lengths.
- Demonstrations and teaching. Seeing that each key is just two sine waves makes a good signal-processing exercise, and the frequency table shows the row and column structure.
- Recognising the sounds. Hearing the tone for each key helps when you are working out what a recorded or remembered sequence was.
- Speaker checks. The tones sit between roughly 700 Hz and 1.6 kHz, within the range most small speakers reproduce, so they work as a quick mid-range sanity check. For a dedicated tool, use the tone generator or the frequency sweep. To check left and right routing first, use the speaker and sound test.
What the A, B, C and D keys are
The fourth column (1633 Hz) holds the keys A, B, C and D. They were used for priority levels on the US military AUTOVON network and are rarely found on consumer phones, though the standard defines them and many decoders and test tools support them. Ordinary phone menus use only 0-9, * and #.
Questions about DTMF tones
What frequencies does each DTMF key use?
Each key plays one low-group tone (697, 770, 852 or 941 Hz, chosen by its row) and one high-group tone (1209, 1336, 1477 or 1633 Hz, chosen by its column). Key 1 is 697 Hz plus 1209 Hz; key # is 941 Hz plus 1477 Hz.
Why does DTMF use two tones instead of one?
A single tone can easily be produced by speech, music or noise. Requiring one tone from each of two separate groups at the same time makes a false detection far less likely.
Can I play these tones into a phone call?
Sometimes, but it is unreliable. The microphone, noise suppression and codec can all weaken or alter the tones, and VoIP systems often expect out-of-band DTMF events rather than audio. Test with the system you actually use and expect mixed results.
What is the difference between DTMF and touch tone?
Touch-Tone was the Bell System's name for push-button dialling that used DTMF signalling. In everyday use the terms are interchangeable.
Does the tool record or send anything?
No. The tones are generated in your browser with the Web Audio API. There is no microphone access, upload or network request involved in playing them.
Sources and technical references
- ITU-T Recommendation Q.23: Technical features of push-button telephone sets
- RFC 4733: RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals
- MDN: OscillatorNode
For a single adjustable frequency, use the online tone generator. For a continuous glide between two frequencies, use the frequency sweep generator. For a steady broadband sound instead of paired tones, use the white, pink and brown noise generator.