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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
● Contaminants expelled by office copying machines
● Highly corrosive
atmosphere within an
enclosed area or atmosphere containing
vaporized chemical compounds that may condense on the equipment
● Explosive or flammable atmosphere
Lighting
I.ighting should be adequate 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.
Electrical Noise (RFI)
In most cases, electrical noise is introduced to the system through trunk or voice terminal
cables. However, electromagnetic fields near the system cabinets may also induce noise in
the system.
Therefore, the system cabinets and cable runs should not be placed in areas
where a high electromagnetic field strength exists.
Radio transmitters (AM or FM),
television stations, induction heaters, motors (with commutators) of 0.25 horsepower (200
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 generally do not cause interference.
Field strengths below 1.0 volt per meter are unlikely to cause interference. Field strength
can be measured by a tunable meter such as the Model R-70 meter manufactured by
Electro-Metrics Division or broadband meters such as the HOLADAY* HI-3001 meter or
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).
* Trademark of Holaday Industries
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