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EFFECTIVEDECEMBER2,1994THEFEDERALGOVERNMENTREQUIRESTHISSTATEMENTTOBEINCLUDED.
ELECTROMAGNETIC INTERFERENCE
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 Radio 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 interfering to
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 unin-
tended directions. It can also permanently damage the powered wheelchair's control system. The
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. 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 elds in the everyday en-
vironment. 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 sources of radiated EMI can be broadly classied 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 talkie," security, re, and police transceivers, cellular telephones, and other
personal communication devices. **NOTE: Some cellular telephones and similar devices
transmit signals while they are ON, even while not being used;
2) Medium-range mobile transceivers, such as those used in police cars, re 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 broadcast
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 wheel-
chair.
Powered Wheelchair Electromagnetic Interference (EMI)