Eicon Networks ISDN NT1 Especificaciones descargar pdf (Pagina 24)

6. Does a Terminal Adapter always contain a Codec or Modem?

A Terminal Adapter does not necessarily need to have a CODEC inside it.

For example, a basic Terminal Adapter could connect a PC via its serial port to an ISDN network without any

requirement for a CODEC.

The bit stream from the serial port is digital, as is the bit stream that goes out to the ISDN. Although a

protocol conversion does indeed occur, it is not an analogue to digital conversion, so no CODEC is required.

On the other hand, when an analogue device, such as a fax machine, needs to be connected, then an

analogue to digital conversion is necessary and a CODEC will be required.

So, simple Terminal Adapters do not need to have CODECs, but they cannot connect analogue devices to

the ISDN.

More sophisticated Terminal Adapters that are able to connect analogue devices to the ISDN do need to

have a CODEC.

7. What are the two options for implementing fax using an internal ISDN card?

To send and receive faxes, an ISDN card needs to perform digital conversions, as if it were an analogue

modem.

It can do this by having an on-board Digital Signal Processor perform the conversion, or it can off-load the

task to the processor of the host PC and use a 'soft modem' application.

The trade-off between the two is that DSP chips are sophisticated technology and are therefore expensive,

whereas using software to perform the conversion can take up a significant amount of the processing power

of the computer.

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Eicon Networks ISDN NT1 Especificaciones Pagina 24