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Metro Power III Owner’s Manual GF0600059RevB06, November 2006
7
ELECTROMAGNETIC INTERFERENCE (EMI) FROM RADIO WAVE SOURCES
It is very important that you read this information regarding the possible effects of electromagnetic
interference on your Everest & Jennings Metro Power III power wheelchair.
Powered wheelchairs may be susceptible to electromagnetic interference (EMI), which is interfering
electromagnetic (EM) energy emitted from sources such as radio stations, TV stations, amateur radio
(HAM) transmitters, two-way radios, and cellular telephones. e interference (from radio wave
sources) can cause the powered wheelchair to release its brakes, move by itself, or move in unintend-
ed directions. It can also permanently damage the powered wheelchair’s control system. e intensity
of the interfering EM energy can be measured in volts per meter (V/m). Each powered wheelchair
can resist EMI up to a certain intensity. is is called its “immunity level”. e higher the immunity
level, the greater the protection. At this time, current technology is capable of achieving at least a 20
V/m immunity level, which would provide useful protection from the more common sources of radi-
ated EMI.
is powered wheelchair model has an immunity level of 20 V/m when tested with Integral Control-
ler Part Number 90762330.
Be aware that using different components, adding accessories, or modifying the powered wheelchair
may change the immunity level.
ere are a number of sources of relatively intense electromagnetic fields in the everyday environ-
ment. Some of these sources are obvious and easy to avoid. Others are not apparent and exposure
is unavoidable. However, we believe that by following the warnings that follow, your risk to EMI
exposure will be minimized.
e sources of radiated EMI can be broadly classified into three types:
1) Hand-held portable transceivers (transmitters-receivers) with the antenna mounted directly on
the transmitting unit. Examples include: citizens band (CB) radios, “walkie talkies”, security, fire,
and police transceivers, cellular telephones, and other personal communication devices.
Note: Some cellular telephones and similar devices transmit signals while they are on, even when not
being used;
2) Medium-range mobile transceivers, such as those used in police cars, fire trucks, ambulances, and
taxis. ese usually have the antenna mounted on the outside of the vehicle; and
3) Long-range transmitters and transceivers, such as commercial broadcast transmitters (radio and
TV broadcast antenna towers) and amateur (HAM) radios.
Note: Other types of hand-held devices, such as cordless telephones, laptop computers, AM/FM radios,
TV sets, CD players, and cassette players, and small appliances, such as electric shavers and
hair dryers, so far as we know, are not likely to cause EMI problems with your powered wheel-
chair.