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dtmf.txt
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1998-03-25
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977b
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31 lines
23. What are the DTMF frequencies?
DTMF stands for Dual Tone Multi Frequency. These are the tones you get when
you press a key on your telephone touchpad. The tone of the button is the
sum of the column and row tones. The ABCD keys do not exist on standard
telephones.
1209 1336 1477 1633
697 1 2 3 A
770 4 5 6 B
852 7 8 9 C
941 * 0 # D
24. What are the frequencies of the telephone tones?
Type Hz On Off
---------------------------------------------------------------------
Dial Tone 350 & 400 --- ---
Busy Signal 480 & 620 0.5 0.5
Toll Congestion 480 & 620 0.2 0.3
Ringback (Normal) 440 & 480 2.0 4.0
Ringback (PBX) 440 & 480 1.5 4.5
Reorder (Local) 480 & 620 3.0 2.0
Invalid Number 200 & 400
Hang Up Warning 1400 & 2060 0.1 0.1
Hang Up 2450 & 2600 --- ---