Adtran L128 用户手册

61202.070L1-1

Express L128/L128T User Manual

Chapter 1

Understanding ISDN and

the Express L128/L128T

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 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.