Functional Description; Control Unit Operation - AT&T MERLIN LEGEND System Reference Manual

Functional Description

Control Unit Operation

Functional Units
This chapter describes the internal functioning of the communications system,
including control unit operation, system modes of operation, line/trunk and
station module operation, system alarms, and power failure transfer.
The control unit contains the following functional units:
the processor module
the carrier
the power supply module
the line/trunk and station modules
This section describes the control unit functional units, their relationships, and
how signals are processed.
The functional units are the processor module, which controls the operation of
the system and its features; the power supply module, which supplies power to
the control unit; the carrier with its backplane assembly, which contains the
input/output (I/O) bus and the time-division multiplex (TDM) bus; and the
line/trunk and station modules, which connect the outside lines/trunks to the
stations. All the modules are electrically connected to the backplane, which
provides common circuitry for the I/O bus, the TDM bus, and power distribution.
(See Figure 4-1 for a functional block diagram of the system architecture.)
The processor module is connected to intelligent ports on the line/trunk and
station modules, through the I/O bus, by the digital switch element (DSE) on
each line/trunk and station module. The TDM bus also is connected to the DSE
of each line/trunk and station module. The two busses are illustrated in
Figure 4-1 and described on the following page.
Control Unit Operation 4-1