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DTMF Tone Generator - Phone Keypad Tones Online
Generate DTMF dual-tone multi-frequency signals for any phone keypad symbol (0-9, *, #, A-D). Click keys to dial and hear the tones in your browser.
Hold a key to sustain the tone. Frequencies shown are row/column Hz.
What is DTMF?
Dual-Tone Multi-Frequency (DTMF) signaling encodes each keypress as a combination of two simultaneous sine waves — one from a low-frequency row and one from a high-frequency column. Using two tones instead of one makes accidental triggering much harder: background noise or a voice is extremely unlikely to match both frequencies at exactly the right moment.
DTMF frequency table
| 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 |
History
DTMF was developed by Bell Labs and introduced commercially in 1963 as Touch-Tone dialing, replacing the older pulse-dialing system where a rotary dial interrupted the line current to count pulses. Touch-Tone was faster — dialing a 7-digit number took roughly 1 second versus up to 10 seconds with pulse — and the two-tone encoding was robust enough to survive the noise and signal degradation common on long-distance telephone circuits of the era.
The A, B, C, D column
The 1633 Hz column — keys A, B, C, and D — was part of the original Bell Labs specification but was never included on consumer telephone handsets. These tones were used in military radio networks (AUTOVON), telephone switching infrastructure, and specialized test equipment. They remain part of the DTMF standard today and are still active in some two-way radio systems, where they are used to address specific radios or trigger repeater functions.
Where DTMF is used today
Despite being over 60 years old, DTMF is still in active use. Interactive Voice Response (IVR) systems — the "press 1 for billing, press 2 for support" menus — rely on DTMF to detect which option a caller selected. Fax machines use a DTMF handshake tone sequence during call negotiation. VoIP systems transmit DTMF either in-band (as audio) or out-of-band via RFC 2833 packets to avoid tone degradation through audio compression codecs. This tool generates tones in-band, making it useful for testing IVR systems, telephony applications, and audio pipelines that need to detect and decode DTMF input.