Multi-Tech Systems ISI5634PCI/4/8 Manual de usuario descargar pdf (Pagina 94)

ISI5634PCI/4/8 User Guide

About DTMF

DTMF (dual tone multi frequency) is the signal to the phone company

that you generate when you press an ordinary telephones touch keys.

In the United States and perhaps elsewhere, its known as

Touchtone phone (formerly a registered trademark of AT&T). DTMF

has generally replaced loop disconnect (pulse or rotary) dialing.

With DTMF, each key you press on your phone generates two tones

of specific frequencies. So that a voice cant imitate the tones, one tone

is generated from a high-frequency group of tones and the other from a

low frequency group. Here are the signals you send when you press

your touchtone phone keys:

tigiD

woL

qerF

hgiH

qerF

1zH796zH9021

2zH796zH6331

3zH796zH7741

4zH077zH9021

5zH077zH6331

6zH077zH7741

7zH258zH9021

8zH258zH6331

9zH258zH7741

0zH149zH6331

*zH149zH9021

#zH149zH7741

When any key is pressed, both the high and low tones of of the row

are generated, hence the name dual tone. For example, pressing the

5 button generates the tones 770Hz and 1336Hz. 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).

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Multi-Tech Systems ISI5634PCI/4/8 Manual de usuario Pagina 94