Isdn Connection; Figure 1-7: Express Xl/Xlt Rear Panels - ADTRAN Express XL 1200070L1 User Manual

Chapter 1: Understanding ISDN and the Express XL/XLT

ISDN Connection

From the network, ISDN is delivered by a single 2-wire 2B1Q U-interface
which is connected directly to the Express XL/XLT. ISDN network termina-
tion is designed into the Express XL/XLT, eliminating the need and expense
of a separate NT1. For network testing, the Express XL/XLT responds to NT1
test commands from the telephone company central office (CO).
The Express XL/XLT has one RJ-45 jack, labeled ISDN BRI U on the rear panel
for network connection (see Figure 1-7). ISDN basic rate service divides a stan-
dard telephone line into three digital channels capable of simultaneous voice
and data transmission. The three channels are comprised of two bearer (B)
channels at 64 kbps and one data (D) channel at 16 kbps, known as 2B+D.
The Express XL/XLT also supports a leased digital connection allowing data
to be transferred at up to 144 kbps over a 2-wire facility using the same RJ-45
jack. This type of service is a permanent connection between endpoints and is
sometimes referred to as a leased connection, a dedicated connection, a nailed-
up connection, or a private circuit. Leased connection or leased line is used in
this manual to represent these types of services.
18
ISDN
TO
BRI U
MAINTENANCE
NIC HUB
ISDN
BRI U PHONE TO
MAINTENANCE
NIC HUB
Express XL/XLT User Manual
TO
10BT
POWER
1200070L1
TO 10BT
POWER
1200070L2
Figure 1-7
Express XL/XLT Rear Panels
61200.070L1-1