Electrical Noise/Radio-Frequency Interference - Lucent Technologies MERLIN LEGEND Release 7.0 System Planning Manual

MERLIN LEGEND Communications System Release 7.0
System Planning 555-670-112
1 Before You Begin
Confirming the Location of the Control Unit
!
For most surge occurrences, the following standard grounding requirements
provide adequate lightning and power surge protection:
Properly wired, grounded, and bonded outside line protectors.
Properly wired and grounded AC outlet.
Properly grounded single-point ground bar.
Properly wired connection between single-point ground and power supply.

Electrical Noise/Radio-Frequency Interference

In most cases, electrical noise is introduced to the system through lines/trunks or
telephone cables. However, electromagnetic fields near the control unit may also
induce noise in the system. The control unit and cable runs, therefore, should not
be placed in areas where a high electromagnetic field strength exists. Radio
transmitters (AM and FM), television stations, induction heaters, motors (with
commutators) of 1/4 horsepower (200 watts) or greater, and similar equipment are
leading causes of interference. Small tools with universal motors do not generally
cause a problem when operated on separate power lines. Motors without
commutators generally do not cause interference.
Field strengths below 1.0 volt per meter are unlikely to cause interference.
Estimate the field strength produced by radio transmitters by dividing the square
root of the emitted power (in kilowatts) by the distance from the antenna in
kilometers.
This yields the approximate field strength in volts per meter and is relatively
accurate for distances greater than about half a wavelength (492 feet, or 150
meters, for a frequency of 1000 Hz).
CAUTION:
Improper ground can result in equipment failures and service
outages. Verify that the AC power uses an approved ground for its
primary ground and that all voltage-limiting devices are attached to
an approved ground. Approved grounds are as follows:
The metal frame of the building.
A metal water pipe connected to an underground water pipe
that is in direct contact with earth.
An electrode encased by at least 2 inches (5 cm) of concrete
and located within and near the bottom of a concrete
foundation or footing in direct contact with earth.
A copper ring that encircles the building and is in direct
contact with earth.
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Issue 1
April 1999
1-5