Unit installation

Installation and Operation Manual Chapter 1 Introduction
FCD-E1 Functional Description 1-11
The receive path of the framer extracts the payload data, the inband management
data stream and demultiplexes the incoming E1 data stream.
The framer also collects performance statistics based on framing errors and errors
detected by the CRC-4 monitoring function, which can be read by the
management subsystem through the module management subsystem.
When the main link is operated in the unframed mode, the framer is bypassed. As
a result, the main link transparently transfers the data stream received from the
data channel. Since in the unframed mode the data channel is configured for
operation at a data rate of 2048 kbps, any other FCD-E1 ports must be
disconnected from the main link.
LIU (Line Interface Unit)
This section describes in detail the operation of the LIU for the electrical main link
interface. The functionality of the optical LIU is similar to that of the electrical LIU,
except that the interface transmits and receives optical signals (see Optical Main
Link on page 1-3).
Transmit Path
The transmit path of the LIU includes an HDB3 coder, which converts the NRZ
transmit data stream provided by the E1 framer to the line code specified for use
on E1 links, and then generates the E1 transmit signal in accordance with ITU-T
Rec. G.703.