Lucent Technologies MERLIN LEGEND 6 - Manual (Page 403)

MERLIN LEGEND Communications System Release 6.0
System Manager’s Guide
555-660-118
Issue 1
February 1998
About Telecommunications
Page B-5 Switching Equipment
B
As noted earlier in this guide, the differentiation between the terms line and trunk
has blurred and the two terms are now often used interchangeably.
The services provided by channels can greatly enhance a company’s
effectiveness and efficiency. If the MERLIN LEGEND Communications System
has a DS1 facility as one of its incoming trunks, the one facility provides 24 “lines”
that are called
channels or B-channels, depending on the type of service the
facility is programmed for (T1 or PRI). If programmed for T1 service, the channels
can be configured to emulate different types of trunks (loop-start, ground-start,
DID, and tie) according to business needs, and can provide a variety of special
services. If programmed for PRI service, additional special services are available
and each B-channel can be programmed to dynamically provide different services
over the same B-channel.
Switching Equipment 2
The primary function of switching equipment is to interconnect the transmission
facilities at various key locations and route the telephone signals through the
telephone network. The telephone network is composed of a number of these key
centralized locations called central offices (COs). At the COs, the electrical signal
carried on one telephone circuit is connected, or switched, to another circuit,
forming a communications path; that is, the caller’s line is connected to the called
party’s line so they can hold a conversation.
In the early telephone network, switching was performed manually by human
operators. Today, electronic computer-controlled switching systems are fast,
flexible, and economical, providing reliable, efficient, and cost-effective service.
There are now also private switches that, rather than being located at the
telephone company’s CO, are located on a company’s premises. These systems,
called private branch exchanges (PBXs), were developed because most of a
business’ calls are between telephones on-site within the company. The MERLIN
LEGEND Communications System is a such a switch, located on the customer’s
premises, that provides advanced services and features and yet also provides
many of the special functions originally performed by human operators.
The Evolution of Switches 2
The method, type, capabilities, and capacities of switches have evolved as
geographic areas expanded and technological advances became available.