AT&T MERLIN LEGEND Installation & Maintenance Manual page 38

System Description
The main board contains the 68000 microprocessor, a built-in
1200-baud data modem, built-in diagnostics, RAM, a real-time
clock, and interrupt circuitry, and interfaces to the other modules
through the I/O bus on the carrier backplane.
The processor module has two modular RS-232 jacks: one for
Station Message Detail Recording (SMDR) and the other for
system programming and maintenance via a personal computer
(see Figure 3).
A NiCad battery in the processor module provides backup
power for the real-time clock and nonvolatile RAM in case of
power failure or system shutdown. The battery provides RAM
data retention for 12 to 30 days. The trickle-charge circuit can
recharge the battery to 50 percent of capacity from a discharged
state in 48 hours. The minimum battery life is five years.
Line/Trunk and Station Modules
The line/trunk and station modules have jacks for connecting the
CO lines/trunks and the station lines to the CU. The station lines
connect to telephones and adjuncts.
Depending on the mode of operation chosen, the outside lines
that extend from the CO are called either trunks or lines. "Trunks"
is used for the Hybrid/PBX mode and in the phrase "tie trunks."
"Lines" is used for Key or Behind Switch modes.
Control Unit 1-7