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Tech Stuff - DTMF Tones

The following table defines the tones used in DTMF (see ANSI T1.401-1988 Section 7.2):

Each tone is composed of a low-high pair of frequencies as defined in the table:

DTMF Char Low (Hz) high (Hz)
1 697 1209
2 697 1336
3 697 1477
4 770 1209
5 770 1336
6 770 1477
7 852 1209
8 852 1336
9 852 1477
* (star) 941 1209
0 941 1336
# (num) 941 1477
A 697 1633
B 770 1633
C 852 1633
D 941 1633

DTMF Tone Power is given by the following table:

Power dBm
Max. Power per tone +1.0
Min. Power per Low freq. tone -10.5
Min. power per High freq. tone -8.5

Notes: frequency limit is +- 1.5%, difference in power between the low and high frequencies should not exceed 3dB and the power of the high frequency tone should equal or exceed the low frequency tone.



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