DTMF Tone Generator

What DTMF tones are

DTMF stands for dual-tone multi-frequency. When you press a key on a phone, it plays two tones at the same time: one from a low group (697, 770, 852 or 941 Hz) for the key's row and one from a high group (1209, 1336, 1477 or 1633 Hz) for its column. The 5 key, for example, is 770 Hz plus 1336 Hz. The exchange or the voice menu listens for that exact pair, which is why a single whistle or a voice doesn't dial by accident. The Bell System introduced it to the public as Touch-Tone dialing in 1963, and the frequencies are standardized internationally in ITU-T Recommendation Q.23.

This DTMF tone generator online plays the phone keypad tones exactly as a phone would: both tones of each key, from the browser's own audio engine. Hold a key to keep the touch tone going, press several in a row, or use your computer keyboard: the digit keys, * and # play the matching DTMF tones while the page is open.

DTMF frequency chart

The DTMF frequencies were chosen so that no tone is a simple multiple of another, which keeps harmonics from one tone from looking like a different key. The fourth column (A, B, C and D) isn't on normal phones; it was used for call priority on the US military AUTOVON network and still turns up on radio and test equipment.

Dial a whole number

Type a number in step 2, including * and #, and press Play. The tone and pause sliders set the timing from 40 to 500 ms. Phone systems are usually designed to accept tones of about 40 ms or longer, so the default of 100 ms tones with 100 ms pauses is a safe choice; slow down for older or noisy receivers. As a phone number tone generator it skips anything that isn't a DTMF key, such as spaces, dashes and brackets, so you can paste a number as it is written.

Unlike a simple DTMF generator that only plays single keys, Download WAV saves the same sequence as a mono 16-bit, 44.1 kHz file, which is handy for testing an answering machine or a voice menu, programming a radio, or playing the tones from another device. The file is created in your browser and nothing is uploaded.

What people use touch tone generators for

• Testing phone menus and equipment: check that an IVR, a door entry system or a PBX reacts to each key.
• Amateur radio: many repeaters and remote controls take commands as DTMF tones.
• Teaching: hear how two frequencies combine and why telephone keypad sounds differ from key to key.
• Sound checks: the 697 to 1633 Hz range sits in the middle of what small speakers reproduce well.

For a single frequency of your choice, from 1 Hz to 22 kHz, use the online tone generator instead.

How we tested this tool

We rendered all 16 keys at 44.1 kHz and measured each 100 ms tone with a Goertzel filter, the same method DTMF receivers commonly use, at all eight DTMF frequencies. For every key the two strongest frequencies were exactly the expected pair, and the strongest of the other six was about 30 dB lower. A dialed test number, 5551234#, came out as 8 tones and 8 pauses of exactly 4410 samples each, the pauses were fully silent, and the peak level stayed at full scale without clipping. The downloaded file had a valid WAV header: mono, 16-bit, 44,100 Hz. In the page we pressed keypad buttons and keyboard keys and checked that the right frequency pair was played and highlighted in the chart, that letters such as "hello" give an error message, and that brackets, spaces and dashes in a pasted number are skipped. We tested in Chrome on desktop and at a 375 px phone width; we did not dial a real phone line or IVR with it.

Frequently asked questions