high-power telephones can cause spurious characters to
appear on the system's monitor screen.
RFI is defined as any EMI with a frequency above
10 kilohertz (kHz). This type of interference can travel
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 each drive bay has 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.
C-4
Dell PowerEdge 4100/180 and 4100/200 Systems User's Guide
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 5 gravities (G) for up to
11 milliseconds (ms). In storage, the system can with-
stand shock pulses of 20 G with a velocity change of
1397 millimeters (mm) per second (55 inches per
second).
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 300 hertz
(Hz) for 15 minutes. In storage, the system can withstand
0.5 G at 3 to 300 Hz for 15 minutes.