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Overview
2-3
Installing the Control Unit
WARNING:
Do not install the control unit outdoors.
Electrical Noise/Radio-Frequency
Interference
2
In most cases, electrical noise is introduced into the system through trunk or
telephone cables. However, electromagnetic fields near the control unit can
also cause noise in the system. Therefore, you should not place the control unit
and cable runs in areas where a high electromagnetic field strength exists.
Radio transmitters (AM and FM), television stations, induction heaters, motors
(with commutators) of 0.25 horsepower (200 watts) or greater, and similar
equipment are leading causes of radio-frequency interference (RFI). Small
tools with universal motors are generally not a problem when they operate 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. To
estimate the field strength produced by radio transmitters, divide (
÷
) the square
root (
√
) of the emitted power, in kilowatts, by the distance from the antenna, in
kilometers, which equals (
=
) the field strength in volts per meter.
Example:
√
49 kw
=
7 kw
÷
10 km (6.2 miles) = 0.7 volts per meter
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 m,
for a frequency of 1000 Hz). If the result exceeds 1.0 volt per meter, you may
have to install shielded cables and/or Z200A filters. See Appendix A,
“Customer Support Information,” in Maintenance and Troubleshooting, for FCC
Part 15 radio frequency regulations.
Содержание Lucent Technologies MERLIN MAGIX
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