OfficeServ 7400
INSTALLATION
TECHNICAL MANUAL
PART 1 MAY 2010
1.3
Bare, covered, or insulated grounding conductors are acceptable. A covered or insulated
grounding conductor shall have a continuous outer finish that is either green or green with
one or more yellow stripes.
Failure to provide an adequate ground may cause a safety hazard, confusing trouble
symptoms, or even circuit card failure.
WARNING
: Unplug the power cord from the AC outlet before attempting to connect the
ground. Hazardous voltage may cause death or injury. Observe extreme caution when
working with AC power. Remove lines from trunk cards.
What the above paragraphs mean is that when conventional analog telephone circuits are
connected to the OfficeServ 7400 system, under fault conditions (i.e., 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 into the
OfficeServ 7400 cabinet(s) from the outside plant (i.e., overhead cables, buried cables, 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 OfficeServ 7400
system to drain this energy off. Again, a good earth ground source is required by the
OfficeServ 7400 system.
The OfficeServ 7400 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 method approved by the National Electrical Code to the
OfficeServ 7400 system ground lug. 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 OfficeServ 7400 system and also for operational reasons to
accommodate ground return and/or ground-referenced analog telephone circuits, which
require this solid earth ground connection for normal functioning.
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