AT&T MERLIN LEGEND Release 3.1 System Manager's Manual page 76

Control Unit
Carriers
The carriers in the system are the containers that hold the modules on which the
circuit boards and connections for lines/trunks and extensions (called jacks or
ports ) are. There can be up to three carriers: one basic carrier and two
expansion carriers.
The carriers hold the modules in slots. For the purposes of system programming
and installation, 2-digit numbers indicate the slots, starting with 00 for the
processor module.
Inside the back of each carrier is a component called the backplane , which
holds the circuitry that makes it possible for the modules to "talk" to each other
and for the processor module to handle the traffic among the modules.
Every system has a basic carrier that holds the following modules in its slots:
Power supply module (not numbered)
Processor module (slot 00)
Up to five line/trunk and extension modules (slots 01–05)
If you need more trunks and/or extensions than can fit in the basic carrier, you
can connect up to two expansion carriers to the basic carrier. Like the basic
carrier, each expansion carrier's leftmost slot holds a power supply module; the
remaining six slots hold line/trunk and extension modules. (The processor
module in the basic carrier serves the expansion carriers too.) The six slots for
line/trunk and extension modules in the expansion carriers are numbered as
follows:
First expansion carrier: slots 06 11
Second expansion carrier: slots 12 17
Processor Module
The processor module is the "brains" of the system, a miniature computer that
controls system features and diagnostics, as well as the traffic among the
modules (see Figure 3 1). The processor module provides three jacks, one for
Station Message Detail Recording (labeled SMDR ), one for system
programming and maintenance using a PC (labeled ADMIN ), and one for
software maintenance by AT&T technicians only (this one is plugged shut).
The Personal Computer Memory Card International Association (PCMCIA)
interface slot on the processor module is the place in which you insert a
PCMCIA memory card. A memory card is very similar to a floppy diskette used
in a PC, but it is about the size of a credit card. There are different types of
memory cards used with the system, each with a different label; see the next
section for more information.
3–2
System Components