Hardware Reference
In-Depth Information
these items can draw an excessive amount of current and wreak havoc with a PC system
on the same electrical circuit. I've seen offices in which all the computers begin to crash
at about 9:05 a.m. daily, which is when all the coffee makers are turned on!
Anothermajorprobleminsomecompaniesispartitionedoffices.Manyofthesepartitions
are prewired with their own electrical outlets and are plugged into one another in a sort
of power-line daisy-chain, similar to chaining power strips together. The person in the cu-
bicle at the end of the electrical daisy-chain is likely to have power problems.
Radio-Frequency Interference
Radio-frequencyinterference(RFI)iseasilyoverlookedasaproblemfactor.Theinterfer-
ence is caused by any source of radio transmissions near a computer system. Living next
door to a 50,000-watt commercial radio station is one sure way to get RFI problems, but
less-powerful transmitters can cause problems, too. I know of many instances in which
cordless telephones have caused sporadic random keystrokes to appear, as though an in-
visibleentityweretypingonthekeyboard.IalsohaveseenRFIcauseasystemtolockup.
Solutions to RFI problems are more difficult to state because every case must be handled
differently. Sometimes, simply moving the system eliminates the problem because radio
signals can be directional in nature. At other times, you must invest in specially shielded
cables for external devices, such as the keyboard and the monitor. If the keyboard or
mouse is wireless, RFI can be especially problematic; the only solution might be to try a
different brand or model that operates on a different frequency.
One type of solution to an RFI noise problem with cables is to pass the cable through a
toroidalironcore,adoughnut-shapedpieceofironplacedaroundacabletosuppressboth
the reception and transmission of electromagnetic interference (EMI). Many monitors in-
clude a toroid (sometimes spelled
torroid
) on the cable that connects to the computer. If
you can isolate an RFI noise problem in a particular cable, you often can solve the prob-
lem by passing the cable through a toroidal core. Because the cable must pass through the
center hole ofthe core, it often is difficult, if not impossible, to add a toroid to a cable that
already has end connectors installed.
RadioShacksellsaspecialsnap-togethertoroiddesignedspecificallytobeaddedtocables
already in use. This toroid looks like a thick-walled tube that has been sliced in half. You
simply lay the cable in the center of one of the halves and snap the other half over the
first. This type of construction makes adding the noise-suppression features of a toroid to
virtually any existing cable easy.
The best, if not the easiest, way to eliminate an RFI problem is to correct it at the source.
It is unlikely that you'll be able to convince the commercial radio station near your of-
fice to shut down, but if you are dealing with a small radio transmitter that is generating
