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Instruction manual

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ENVIRONMENTAL REQUIREMENTS
Air Purity
The cabinet should not be installed in an area where the air may be contaminated with any of the
following:
Excessive dust, lint, carbon particles, paper fiber contaminants, or metallic contaminants
Corrosive gases, such as sulfur and chlorine
Lighting
Lighting should be bright enough to allow administration and maintenance personnel to perform
their tasks. The recommended light intensity level is 50 to 70 footcandles. This level complies
with the Occupational Safety and Health Act (OSHA) standards.
Noise
In most cases, electrical noise is introduced into the system through trunk or station cables, or
both. However, electromagnetic fields near the system control equipment may also cause noise
in the system. Therefore, the system and cable runs should not be placed in areas where a high
electromagnetic field strength exists. Radio transmitters (AM or FM), television stations, induc-
tion heaters, motors (with commutators) of 0.25 horsepower (187 watts) or greater, and similar
equipment are leading causes of interference. Small tools with universal motors are generally not
a problem when they operate on separate power lines. Motors without commutators, whether
synchronous or asynchronous, generally do not cause interference.
Field strengths below 1.0 volt per meter are unlikely to cause interference. These weak fields
can be measured by a tunable meter such as the Model R-70 meter manufactured by Electro-
Metrics Division.
Field strengths greater than 1.0 volt per meter can be measured with a broadband meter such as
the HOLADAY
TM
HI-3001 meter or the Model EFS-1 meter manufactured by Instruments for
Industry, Inc.
The field strength produced by radio transmitters can be estimated 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 (150 meters for a frequency of 1000 kHz).
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