which is interfering electromagnetic energy emitted from sources such as radio
stations, TV stations, amateur radio (HAN) transmitter, 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
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 “immunity level”. The higher the
immunity level, the greater the protection. At this time, current technology is capable
of providing at least 20 V/m of immunity level, which would provide useful
protection against common sources of radiated EMI.
Following the warnings listed below should reduce the chance of unintended brake
release or powered wheelchair movement that could result in serious injury:
1,Do not turn on hand-held personal communication devices such as citizens band(CB)
radios and cellular phones while the powered wheelchair is turned on.
2.Be aware of nearby transmitters such as radio or TV stations and try to avoid
coming close to them.
3.If unintended movement or brake release occurs, turn the powered wheelchair off as
soon as it is safe.
4.Be aware that adding accessories or components, or modifying the powered wheel-
chair, may make it more susceptible to interference from radio wave sources
(Note: It is difficult to evaluate the effect on the overall immunity of the powered
wheelchair).
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.Report all incidents of unintended movement or brake release to the powered
wheelchair manufacturer, and note whether there is a radio wave source nearby.
TURN OFF YOUR POWERED WHEELCHAIR AS SOON AS POSSIBLE WHEN
EXPERIENCING THE FOLLOWING:
•
Unintentional motions
•
Unintended or uncontrollable direction.
•
Unexpected brake release
The FDA has written to the manufacturers of power wheelchairs asking them to test
new products to be sure they provide a reasonable degree of immunity against EMI.
The FDA requires that a powered wheelchair should have an immunity level at least
20 V/m, which provides a reasonable degree of protection against more common
sources of EMI. The higher the immunity level, the greater the protection. Your
powered wheelchair has an immunity level of 20 V/m which should protect against
common sources of EMI.
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