Dual-Tone Multi-Frequency (DTMF) is the signal that you generate when you press an ordinary telephone's touch keys. Over the years, DTMF has replaced Pulse dialing, the early type of telephone dialing in which short pulses were used to relay the dialed number. With DTMF, each keypress on your phone generates tones made of two specific frequencies.
|1209 Hz||1336 Hz||1477 Hz||1633 Hz|
The frequencies were chosen to avoid harmonics : no frequency is a multiple of another, the difference between any two frequencies does not equal any of the frequencies, and the sum of any two frequencies does not equal any of the frequencies. Although DTMF works in normal human voice range, the combination of inharmonic frequencies makes it hard for the human voice to impersonate.
Although mobile phone networks use digital signals instead of DTMF for direct dialing, DTMF is still used over mobile phones to navigate automated systems such as phone menus, voice menus and other advanced calling services.
Generating and downloading uncompressed files has a cost to me. Help me keeping this feature alive by supporting my work. Thank you!
File output is telephone quality (8 kHz, .wav file), -1dBFS output level, 100ms per digit, 1s for a pause (space character).
Is AudioCheck free? Not for me. Your support keeps this site running and growing without ads. Every donation gets rewarded with an access to • uncompressed .wav files downloads, for every test • sample rates up to 192 kHz, in the tone generator section • a suggestion box, on every page • no ads, never.
If you already are a patron, please log in.