AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 77

Hardware Components
The processor 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 (PC) with SPM software (see Figure 2-2).
Figure 2-2, Processor Module
A NiCad battery in the processor 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.
Power Supply Module
The power supply provides power to the carrier, to each telephone, and to
adjuncts—except for adjuncts such as answering machines and fax machines,
which come with their own power supplies. Each carrier requires its own power
supply module, which goes into the leftmost slot on each carrier.
The power supply converts 117-VAC line voltage to these outputs: +5 VDC, -5
VDC, and -48 VDC. All modules use +5 VDC and -5 VDC for logic circuits.
Most line/trunk and station modules use -48 VDC for power to the stations. The
Direct Inward Dialing (DID) and off-premises telephone (OPT) line/trunk and
station modules also provide -48 VDC on the tip/ring (T/R) interface to the
telephone company's central office (CC)) or OPT station. The 012 module basic
telephone module provides 21 VDC to single-line telephones and equipment.
Control Unit 2-3