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DTMF Tones
dialabc · sound · dtmf

DTMF Tones

The sounds used for touch tone dialing are refered to as DTMF (Dual Tone Multiple Frequencies) tones. Each number (as well as the "#" and "*") is represented by a pair of tones. For instance, the number "1" is represented by the frequencies 1209 Hz and 697 Hz.

The following table shows the DTFM frequencies and the corresponding keys.

Key Frequency #1 Frequency #2
1 697 Hz 1209 Hz
2 697 Hz 1336 Hz
3 697 Hz 1477 Hz
A 697 Hz 1633 Hz
4 770 Hz 1209 Hz
5 770 Hz 1336 Hz
6 770 Hz 1477 Hz
B 770 Hz 1633 Hz
7 852 Hz 1209 Hz
8 852 Hz 1336 Hz
9 852 Hz 1477 Hz
C 852 Hz 1633 Hz
* 941 Hz 1209 Hz
0 941 Hz 1336 Hz
# 941 Hz 1477 Hz
D 941 Hz 1633 Hz

DTMF "Touch" Tones are defined in CCITT Volume VI: General Recommendations on Telephone Switching and Signalling Recommendation Q.23: Technical Features of Push-Button Telephone Sets."

 
Last updated Monday July 15 2002
For more info contact Helmut Hissen.
(C) Copyright 1996-2002 by Helmut Hissen
All rights reserved.