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Cabling

In this section you will learn about

• Wiring requirements for BRI and PRI

• Maximum cable lengths

• How to connect several devices to a BRI

• When you need to use termination

• The power sources available through the interface

What you get with ISDN

EuroISDN is now the standard in most parts of the world, except North America and

certain other countries.

The EuroISDN network is supplied to the user through a box mounted on the all. This box

is called a Network Termination Type 1 or NT1.

The NT1 is part of the network and is the point at which the network service is supplied.

In North America (and some other countries) ISDN is supplied as a passive socket

terminating the circuit to the ISDN service provider.

Cabling from NT1

All the wiring on the user's side of the NT1 is the user's responsibility. Your ISDN service

supplier is unlikely to be able to help you with any problems you have here.

In the case of the BRI NT1, the standard (I.430) is very specific. You must use RJ45 plugs

(although the standard does not express it in exactly these terms). These are most

commonly found in structured wiring systems based on Category 5 twisted pair. This

standardisation is very important because you can connect as many as eight devices to a

BRI NT1.

If your NT1 is providing a PRI, you will have to use whatever cables are suitable for the

sockets that are provided. Unfortunately, these are can vary according to the ISDN

supplier. They might be two miniature co-axial sockets, RJ45 sockets, or even screw-down

connections. The standard that covers this (I.431) allows some leeway. This not usually a

major problem, since you are allowed to connect only one device to a PRI NT1.

In the discussion below, all the distances cited assume that you are using Category 5

cabling. However, other types of cabling are also suitable such as AT&T PDS, Category 4,

and Category 3.

In addition, these measurements apply only to the BRI. I.430 makes no mention of any

distances at all - it only describes what the characteristics of the wiring should be. The

lengths of the cables contribute to these characteristics. You may therefore see other

values for distances quoted in other sources. Neither source is necessarily wrong, it just

depends on the type of cable that you're using.

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Eicon Networks ISDN NT1 Specifiche Pagina 47