AT&T MERLIN LEGEND Installation & Maintenance Manual page 37

System Description
Power Supply Modules
The power supply module provides power to the carrier, to each
telephone, and to adjuncts— except for adjuncts such as
answering machines and fax machines that have their own
power supplies. Each carrier requires its own power supply
module, which goes into the first slot on the carrier.
The power supply module 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 and analog transmission 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 CO or OPT station.
The 012 basic telephone module provides 21 VDC to single-line
telephones and equipment.
When single-line telephones are connected to a 012, 800 DID, or
008 OPT module, a 129B Frequency Generator (ring generator)
must be installed in the power supply module of each carrier that
houses one or more of these modules.
A green light on the power supply module remains on as long as
the module is receiving power. The power supply module also
has an on/off switch and a modular telephone jack for
connecting an auxiliary power unit as needed (see Figure 3).
Processor Module
Placed in slot 00 of the basic carrier, the processor module
controls system features and programming via the processor
and memory boards and the feature module. The processor
module comes in small and large versions. The small processor
module supports up to 24 CO or tie lines/trunks and 56 stations.
The large processor module supports up to 80 CO or tie
lines/trunks and 144 stations.
1-6 Control Unit