Telephone Tones
A source of innocent merriment!
(W.S. Gilbert)
Dual Tone Multi Frequency
DTMF tones are used for ``dialling'' a number. Each digit is signalled by a 100ms
burst of f1+f2 Hz, followed by 100ms silence. Some equipment will accept shorter
pulse durations, or shorter silent durations, but this is not recommended.
The frequencies f1, f2 are given by the following table.
| | 1209 | 1336 | 1477 | 1633
|
| 697 | 1 | 2 | 3 | A
|
| 770 | 4 | 5 | 6 | B
|
| 852 | 7 | 8 | 9 | C
|
| 941 | * | 0 | # | D
|
E.g. digit `5' is signalled by 770+1336 Hz.
Enter a string of digits from the set { 0-9, *, #, A-D } in the space below
for a sample.
Tony Fisher / fisher@minster.york.ac.uk