March 2014

DocID11830 Rev 2

1/16

AN2266

Application note

SLIC based system protection for European and Asian markets

Introduction

Even with the boom of the digital technologies and the wireless systems, telecom analog

lines remain the most used link to carry speech around the world. Following telecom

deregulation the market, traditionally managed by national telecom administrations, is now

open to new operators. This makes for an increase in new applications using this simple

and cost effective way to supply speech signals.

Figure 1 shows the classic analog telecom system topology, where subscriber terminals are

linked to the central office (CO) by means of copper wires. Inside the CO, lines cross the

main distribution frame (MDF) and then are connected to subscriber line cards. In

subscriber line cards, lines are managed by subscriber line interface circuits (SLIC).

Figure 2 shows the new telecommunication system topology. In this case the long distance

carrying of signals is through modern digital lines like optical fiber, coax, WLL, and others,

while the local distribution is still using copper twisted pairs.

Despite the fact that in both cases the subscriber terminal is connected to the SLIC by

means of copper wires, the line length is quite different (a few hundred meters to a few

kilometers for the classic system and a few meters to a few tens of meters for the new

system topology). This difference in length of the subscriber terminal connection makes the

management of the signal amplitude and the SLIC different.

Figure 1. Classic analog telecom system

topology

Figure 2. New telecommunication system

topology

Subscriber

terminal

Subscriber

line cards

Main distribution

frame

Central office

Primary

protection

modules

SLICs

Line

High speed

Digital link

Connection

Boxes

SLICs

Line

Subscriber

terminal

Subscriber

terminal

Subscriber

terminal

Line

Line

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