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CAUTION: IT IS VERY IMPORTANT THAT YOU READ THIS INFORMATION
REGARDING THE POSSIBLE EFFECTS OF ELECTROMAGNETIC INTERFERENCE ON
YOUR POWERED WHEELCHAIR.
Electromagnetic Interference (EMI) From Wave Sources
Powered wheelchairs and motorized scooters (in this text, both will be referred to as
powered wheelchairs) may be susceptible to electromagnetic interference (EMI), which is
interference from
electromagnetic energy (EM) emitted from sources such as radio stations, TV stations,
amateur radio (HAM) transmitters, two-way radios and cellular phones. The interference
(from radio wave sources) can cause the powered wheelchair to release its brakes, move
by itself, or move in unintended directions. It can also permanently damage the powered
wheelchair’s control system. The intensity of the interfering EMI energy can be measured
in volts per meter (v/m). Each powered wheelchair can resist EMI up to a certain intensity.
This is called its “immunity level.” The 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 radiated EMI.
There are a number of sources of relatively intense electromagnetic fields in the everyday
environment. 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
listed below, your risk to EMI will be minimized.
The source 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. Example include: citizens band (CB)
radios, “walkie talkie,” security, fire, and police transceivers, cellular telephones, and
other personal communication devices transmit signals while they are ON, even
while not being used.
2) Medium-range mobile transceivers,
such as those used in police cars, fire
trucks, ambulances, and taxis. These usually have the antenna mounted on the
outside of the vehicle.
3) Long-range transmitters and transceivers,
such as commercial broadcasts
transmitters (radio and TV broadcast antenna towers) and amateur (HAM) radios.
NOTE:
Other types of hand-held devices, such as cordless phones, 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 to
your powered wheelchair.
ELECTROMAGNETIC INTERFERENCE
SECTION 15
