AT&T Partner II - Manual (Page 14)

System Your premises equipment, in combination with the Centrex
lines that are connected to your equipment controller and the
Centrex services that are available on those lines. See also
Centrex system and Premises equipment.
Using Premises Equipment
to Complement Centrex Services
The system discussed in this guide consists of two elements: Centrex services
(including Centrex lines and associated features) and premises equipment
(including the equipment controller, MLS- and MLC-model telephones, and
other telecommunications devices connected to the controller).
The Centrex services you receive from your local telephone company provide a
unified telephone network for your business, even across different geographical
locations, and give you services customized for your needs.
NOTE:
Your telephone company may offer Centrex services under a different name (for
example, ESSX,® CENTRON,® or Plexar®). Also, you may be able to select
different services for different lines. (For more information, see the Centrex
documentation provided by your local telephone company.)
Your AT&T premises equipment is designed to complement the advantages
offered by Centrex. All or some of your Centrex lines may be connected to the
equipment controller. You can connect a maximum of 24 Centrex lines and 24
extensions to your equipment controller. Figure 1-1 shows an example in which
some Centrex lines are connected to the equipment controller and some are not
Public Phone
Network
Centrex
Central
Office
Your Centrex System
Your System
Equipment
Controller
555-1000 555-1001 555-1002 555-1003 555-1004 555-1005
Figure 1-1. Your Centrex System
Overview 1-3