Eicon Networks ISDN NT1 Specifikace stáhnout pdf (Strana 22)

Soft-fax and Soft-modem

This means that an ISDN adapter with an on-board DSP can also communicate with any

device that contains a modem. In the diagram below, you can see that we've added a fax

machine.

To perform the job of a modem and a CODEC at the same requires a large amount of

processing power. DSPs are very powerful processors. Nevertheless, you need one DSP

for each B channel for which you want to use this technique. There is, however, no reason

why you couldn't use an ISDN adapter that has a single DSP and a soft modem driver to

handle two modem calls at a time.

Summary

• In ISDN networks everything is carried as a stream of bits.

• Converting digital telephone signals into voice, and vice versa, is done by CODECs.

• Converting data into analogue telephone signals, and vice versa, is done by

modems.

• A CODEC is the device that allows telephony between an ISDN and the analogue

network.

• This same CODEC can be used to allow modem and fax calls to cross the same

boundary.

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Eicon Networks ISDN NT1 Specifikace Strana 22