Nortel Networks CALLPILOT 555-7101-217 - Manual (Page 48)

Power supply installation Standard 1.0
48 CallPilot
About the Power Distribution Unit
Introduction
A Power Distribution Unit (PDU) is installed in a rack that has DC-powered
servers. Power from the DC supply source enters the PDU and can then be
distributed to one or more servers. A single PDU can supply DC power to
four DC power supply modules. A server can have either one or two power
supply modules installed. You can determine the number of PDUs to install
in a rack by counting the number of power supply modules in each rack.
Multiple PDUs
A server operates on a single power supply module. Its total capacity is two
installed power supply modules. The second power supply module is the
redundant power supply module.
A PDU can distribute power to a maximum of four power supply units that
can be installed in two or more servers. Therefore, if there are three or four
servers installed in a rack, then you must install a second PDU.
Note: The power supply module installs in the server. It does not refer to a
UPS, which is a separate unit on the rack.