DTMF Tone Generator & Decoder

Free DTMF tool for generating and decoding telephone keypad tones in your browser. Includes a 4×4 keypad with the A–D military row, sequence player with adjustable timing, microphone and audio-file decoder, multi-region call-progress tones, and WAV/MP3 export. Built for IVR developers, telecom engineers, ham radio operators, and post-production sound designers.

How to Use

1
Tap or type

Click keypad keys, paste a phone number into the sequence tab, or type 0–9 / * / # / A–D on your physical keyboard.

2
Tune timing

Adjust tone and pause duration with the sliders or pick the ITU Q.23 preset for compatibility with telecom equipment.

3
Decode incoming

Open the Decoder tab, allow microphone access, or drop an audio file — the tool extracts the dialed digits with timestamps.

4
Export

Save the sequence as WAV (8 kHz telephone or 44.1 kHz CD quality) or MP3 — ready for IVR uploads, audio editing, or film post-production.

Dial, decode, and export touch-tones with ITU-Q.23 precision

Press a key to dial
1209133614771633
697770852941
⌨️ Type 0–9, *, #, A–D on your keyboard
No tones yet — type digits or paste a number
Allowed: 0-9 * # A-D · pause: , or space · long wait: w
Drop audio file or click to upload WAV, MP3, OGG, M4A — any browser-supported audio
Decoded sequence will appear here
#TimeKeyLow HzHigh HzConfidence
Detected tones will appear here with timestamps
Region
⚠️ For educational and post-production use only. Generating these tones is legal; transmitting them on public phone networks is illegal in most jurisdictions.
🔴 Red Box · Coin tones
ACTS coin-acceptance tones (1700+2200 Hz). Used by US payphones from the 1960s–80s to signal coin deposits to the central office.
🔵 Blue Box · MF
In-band signaling tones used by 1970s phreaks to seize trunk lines. 2600 Hz disconnected the call; KP/ST framed multi-frequency digit dialing.
⭐ AUTOVON · A–D Precedence
The fourth column (1633 Hz) — A, B, C, D — was used on AUTOVON military telephones to prioritize calls during emergencies. Modern PBXs sometimes still accept these for special routing.
KeyPrecedenceFrequency
AFlash Override697 + 1633 Hz
BFlash770 + 1633 Hz
CImmediate852 + 1633 Hz
DPriority941 + 1633 Hz
Tone duration 100 ms
Pause duration 100 ms
Volume -6 dB
Twist (high vs low tone) 0 dB
Timing preset
Sample rate
Waveform
Spectrum (500–1800 Hz)

Features

Full 4×4 keypad with A–D row, ITU-T Q.23 frequencies (697 / 770 / 852 / 941 × 1209 / 1336 / 1477 / 1633 Hz) Sequence player with adjustable tone and pause (40–500 ms), twist (±12 dB), unlimited length, and shareable URL Microphone and file decoder using the Goertzel algorithm — outputs decoded string plus per-tone timestamps Call-progress tones (dial, busy, ringback, SIT, reorder) for US, UK, EU, RU, JP, AU; historical Red/Blue Box reference Audio export at 8 / 44.1 / 48 kHz via FFmpeg WebAssembly — no watermark, no paywall

FAQ

What is DTMF?

Dual-Tone Multi-Frequency — the touch-tone signaling each phone key emits as a pair of sine-wave frequencies (one low, one high). Standardized by ITU-T Q.23, used since the 1960s on Bell System Touch-Tone phones and now in IVR menus, modems, and ham radio autopatch.

What are the A, B, C, D keys?

The fourth column (1633 Hz) was used by US AUTOVON military telephones for call precedence — A = Flash Override, B = Flash, C = Immediate, D = Priority. Consumer phones omit them, but they remain part of the DTMF standard and are sometimes used by modern PBX systems for special routing.

Can I decode DTMF from a recording?

Yes — open the Decoder tab and either drop an audio file (WAV, MP3, OGG, M4A) or use your microphone live. The decoder outputs the decoded string plus per-tone timestamps, source frequencies, and a confidence score, exportable as CSV.

What is "twist"?

The amplitude difference (in dB) between the high and low tones. The ITU-T allows +4 dB / −8 dB. Many real telecom systems boost the high tone slightly to compensate for line attenuation — the slider lets you simulate that.

Why include historical Red/Blue Box tones?

For education, telecom history enthusiasts, and accurate film/TV post-production. These tones are legal to generate and study; transmitting them on live public phone networks is illegal in most jurisdictions.

What sample rate should I use?

8 kHz matches the bandwidth of the public telephone network — best for IVR uploads. 44.1 kHz is CD quality, 48 kHz is studio standard — best for film, video, and music production.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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