Nortel Meridian 1 Administration And Maintenance page 22

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Chapter 1 — ISDN Basic Rate Interface
553-3011-311 Standard 7.0
The length of an S/T interface DSL depends on the specific terminal
configuration and the DSL wire gauge, however, it should not exceed 1 km
(3280 ft). Refer to Chapter 5 for more information.
Terminal Adapters (TAs), as shown in Figure 3, are used to adapt non-BRI
terminals to ISDN BRI line interface standards.
U interface
The U interface provides 2-wire point-to-point connection over a DSL. Each
U interface provides two B-channels and one D-channel and supports only
one physical termination. This termination may be to a Network Termination
1 (NT1) or directly to a single U interface terminal that contains an internal
NT1. Normally this physical termination is to an NT1, (that supports 2B1Q
line encoding) which provides a conversion from a U interface to an S/T
interface that allows up to eight physical terminals to be connected.
The length of a UILC DSL depends on the specific terminal configuration and
the DSL wire gauge, however, it should not exceed 5 km (16405 ft). When
connected to an NT1 the DSL length is effectively extended to 6 km (19685
ft) and utilizes the multi-terminal capability of an S/T interface.
Figure 4 illustrates a typical ISDN BRI configuration showing an Option 11
with an ISDN BRI U interface. ISDN BRI terminals that comply with NT1
interface requirements can be connected as shown in this diagram.
May 1999