To Next Page

To Previous Page

Chapter 1. System Overview and Modes of Operation

Line Interface Units

Line Interface Units (LIUs) perform the primary multiplexing functions in the D/I Mux III system.

Information from the various line cards is combined and converted to T1 format, and information

from the network is distributed to the line cards, through the LIUs. Circuitry to option various

framing and coding takes place in the LIUs. LIUs also recover and supply T1 clock and framing.

The D/I Mux III system, whose architecture was designed primarily for drop-and-insert operation,

requires the use of two LIUs in every mode of operation. Channel bank mode, where only one T1

is accessed, also requires a pair of LIUs. The two LIUs are slightly different and must be installed

in their designated card slot.

There are three paired versions of LIUs available for the D/I Mux III, depending upon

configuration. They include the standard LIUs for use with twisted-pair cable, the ALPS LIUs,

and the Fiber LIU module for use with fiber optics.

For channel bank, drop-and-insert, or dual channel bank operation, use:

• Line Interface Unit B (T1-1) - Part Number 30309-104A

• Line Interface Unit A (T1-2) - Part Number 30309-114A

For channel bank, drop-and-insert, dual channel bank, with ALPS operation, use:

• ALPS Line Interface Unit B (LIU-B) - Part Number 30309-105

• ALPS Line Interface Unit A (LIU-A) - Part Number 30309-115

Note: ALPS LIUs are not discussed in this manual. Refer to the ALPS User's Manual

for information on the ALPS LIUs.

LIU Functions

The primary functions of the LIUs are as follows.

• Recover clock

• Attenuate jitter

• Detect framing and adjust multi-frame alignment

• Drop data to channel units and insert data into T1 line

• Generate outgoing Alternate Mark Inversion (AMI)

• Provide LEDs for status information

• Provide provisioning ability

• DS0 blocking (30309-105 and 30309-115 LIUs only)

• Provide T1 loop code generation

• Receive loop code from T1; notify CSU interface to loop up

See Figure 1-14 for a detailed LIU block diagram.

Coastcom D/I Mux III System User Manual

Questions and Answers: