Power Connections - Samsung OfficeServ500 Installation Manual

3-2 Chapter 3
Grounding and Power Connections
NOTE ON GROUNDING—When conventional analogue telephone circuits are connected to the system, under certain fault
conditions (e.g., the tip and/or ring conductor is crossed with a power line, or the circuit is affected by lightning during a
storm), it is possible for hazardous potentials to appear across the tip and ring wiring coming in to the system cabinet(s) from
outside (i.e., from overhead cables, buried cables, or cable head pedestal). These circuits are provided with both primary and
secondary protection circuitry which will attempt to drain off these high voltages and currents to earth ground. Obviously, it is
important to have a good source of ground connected to the system to drain this energy off. Also, certain metallic analogue
circuits (e.g., E & M trunks) require a current flow to earth ground to accommodate normal operating conditions and/or to re-
solve fault conditions. Again, a good earth ground source is required by the system.
The telephone system has two ground reference points. One point is via the green wire in the power cord connected to the
AC power outlet. This ground connection is provided to meet local electrical codes when the AC ground is required to be
common with the earth ground. However, this can be disconnected either intentionally or unintentionally. Consequently, a
more permanent ground connection is required by connecting a high current/voltage capacity ground wire which is bonded to
ground at the electric service power entrance or via some other approved method to the system ground bar. This is a more
secure ground connection, which can only be disconnected intentionally. These precautions are taken for safety reasons to
protect personnel working on the system and also for operational reasons to accommodate ground return and/or ground-
referenced analogue telephone circuits, which require this solid earth ground connection for normal functioning.

Power Connections

AC POWER CORD ASSEMBLY
The AC power cord supplied with the cabinet plugs into the AC power input socket located on the left
side of the cabinet
WARNING: Do not connect AC power to the system
INSTALLING POWER SUPPLY UNITS (PSU-B and PSU60)
The PSU-B is the main power supply for the system cabinet(s). A second PSU-B or a PSU60 is re-
quired if more than 56 stations are required. This rule applies to each cabinet.
Before installing a PSU, verify that the power switch is in the proper voltage setting position,
110V or 220V as required
The main PSU-B is installed in the first cabinet slot labelled "PSU-B". A second PSU is installed in the
slot labelled "PSU-B/PSU60". Before a second PSU can be installed, it will be necessary to remove
the safety cover-plate that protects the power socket on the backplane. Undo the screw holding the
cover-plate to remove it.
(Figure 3-2).
(Figure 3-3).