Magnetism; Shock And Vibration; Power Source Interruptions - Dell Precision 400 User Manual

from the computer to other devices through the alternat-
ing current (AC) power cable and power source or
through the air like transmitted radio waves. The Federal
Communications Commission (FCC) publishes specific
regulations to limit the amount of EMI and RFI emitted
by computing equipment. Each Dell system meets these
FCC regulations.
To reduce the possibility of EMI and RFI, follow these
guidelines:
•
Operate the system only with the computer cover
installed.
•
Ensure that all expansion slots are covered either by
a card-mounting bracket or by a metal filler bracket
and that all drive bays have a drive and/or a metal
insert installed. These brackets and metal inserts are
available from Dell.
•
Ensure that the screws on all peripheral cable con-
nectors are securely fastened to their corresponding
connectors on the back of the computer.
•
Always use shielded cables with metal connector
shells for attaching peripherals to the computer.
To prevent the possibility of RFI from a computer affect-
ing TV reception, follow these guidelines:
•
Keep any TV set at least 6 ft away from the com-
puter system.
•
Use cable TV when possible.
•
Use a directional outdoor TV antenna.
•
Attach line filters to the TV set.
•
Use 75-ohm coaxial cable for the TV set rather than
twin-lead antenna wire.
•
If interference occurs, rotate the computer or the TV
set 90 degrees.

Magnetism

Because they store data magnetically, diskettes and hard-
disk drives are extremely susceptible to the effects of
magnetism. Diskettes should never be stored near mag-
netic sources such as the following:
•
Monitors
•
TV sets
•
Printers
•
Telephones with real bells
•
Fluorescent lights

Shock and Vibration

Excessive shock can damage the function, external
appearance, and physical structure of a system. Each Dell
system has been designed to operate properly after with-
standing a minimum of six consecutively executed shock
pulses in the positive and negative x, y, and z axes. Each
shock pulse can measure up to 50 gravities (G) for up to
2 milliseconds (ms). In storage, the system can withstand
shock pulses of 92 G for 2 ms.
Excessive vibration can cause the same problems as men-
tioned earlier for shock, as well as cause components to
become loose in their sockets or connectors. Systems can
be subject to significant vibration when being transported
by vehicle or when operated in an environment with
machinery that causes vibration.
Each Dell system, when operating, is designed to with-
stand 0.25 G (half-sine wave) at a sweep of 3 to 200 hertz
(Hz) for 15 minutes. In storage, the system can withstand
0.5 G at 3 to 200 Hz for 15 minutes.

Power Source Interruptions

Computer systems are especially sensitive to variations
in voltage supplied by the AC power source. Over-
voltage, undervoltage, and transients (or spikes) can erase
data from memory or even cause components to fail. To
protect against these types of problems, power cables
should always be properly grounded and one or both of
the following methods should be used:
•
Use one of the power protection devices described in
the following section, "Power Protection Devices."
•
Place the system on a dedicated power circuit (rather
than sharing a circuit with other heavy electrical
equipment). In general, do not allow the system to
share a circuit with any of the following:
— Kitchen appliances
— Copier machines
— Air conditioners
— Vacuum cleaners
— Space heaters
Maintaining the System D-5