DTMF Tone Generator
Type a number and hear the dial tones a phone keypad would make.
Protect your hearing
Keys 0-9, *, # and A-D. A comma is a pause; spaces and dashes are ignored.
Each key is two sine tones at once, one from its row and one from its column. A tone of about 100 ms with a 50 ms gap is the usual speed for dialing.
The highest point of the wave, relative to digital full scale.
The file is 1.00 s long: it follows from the keys and the timings.
How it works
- Type digits, or tap the keypad.
- Set the tone length and the gap between tones.
- Press Play, or create a file to download.
What it does
DTMF, or touch-tone, signalling is how telephone keypads send digits. Each key is two sine tones played together: one from a row frequency (697, 770, 852 or 941 Hz) and one from a column frequency (1209, 1336, 1477 or 1633 Hz). Type a sequence or press the keypad, play it, and save it as an audio file.
Sequence and timing
Keys are 0 to 9, * and #, plus A to D, which most phones lack. A comma adds a pause, and spaces, dashes and brackets are ignored, so a number can be pasted as it is written. The tone length and the gap between tones are set in milliseconds. About 100 ms of tone and 50 ms of gap is a typical dialing speed. The file length follows from the keys and timings, and every tone has short smooth edges so it does not click.
For telephone audio you can export at 8 kHz, which is the sample rate of a classic phone line.
What it is for
It is meant for testing equipment and software that decodes DTMF, for sound effects and for learning. A recording of tones does not dial a phone call by itself, and it will not work on systems that filter or compress the audio heavily.
Questions
Which two frequencies make which key?
Row frequencies are 697 Hz for 1 2 3 A, 770 Hz for 4 5 6 B, 852 Hz for 7 8 9 C and 941 Hz for * 0 # D. Column frequencies are 1209 Hz for 1 4 7 *, 1336 Hz for 2 5 8 0, 1477 Hz for 3 6 9 # and 1633 Hz for A B C D.
Why do some keys A to D not exist on my phone?
They were designed for special uses and were left off ordinary phone keypads. The tool plays them like any other key.
How do I put a pause in the number?
Type a comma where the pause should be. Each comma adds the pause length you set, 500 ms by default.
Can the tones be decoded again?
Standard decoders should read them at the default timing and the usual sample rates; this tool checks its own output the same way. Very short tones, or heavy compression such as a low-bitrate MP3, can make decoding unreliable.