ADTRAN L128 User Manual
Page 24
61202.070L1-1
Express L128/L128T User Manual
7
Chapter 1
Understanding ISDN and
the Express L128/L128T
ISDN OVERVIEW
The Integrated Services Digital Network (ISDN) is a public or private switched
digital network. ISDN is an international standard for digital communica-
tions, allowing a full range of enhanced services supporting voice, data, and
image applications through standard interfaces over a single telephone wire.
ISDN provides a means of integrating these services and modernizing com-
munication networks for information movement and management efficiency.
THE EXPRESS L128/L128T
The Express L128/L128T is a standalone device that links two Local Area Net-
works (LANs) using a high-speed ISDN public network or leased two-wire
line. Optionally, the Express L128T has two plain old telephone service
(POTS) connectors used for voice/modem applications
See Figure 1-1 for an illustration of the Express L128/L128T. The 10BaseT con-
nector operates at 10 megabits per second half duplex and accepts standard
Ethernet packets encapsulated using IEEE 802.3 or Ethernet II (DIX). Because
the 10BaseT is a four-wire interface, a crossover switch permits the user to con-
nect to either a hub-concentrator or network interface card without the need
for special cabling. The maintenance port can connect to any asynchronous
terminal emulating a VT 100 terminal for configuration.
Figure 1-1
Express L128/L128T
LI
EXPRESS L128T
TX/RX
B1
B2
PWR
LINE
TEST