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14 www.pridemobility.com Jet 3/Rev I/Feb03
Laboratory tests performed by the Food and Drug Administration (FDA) have shown that radio waves can cause
unintended motion of power chairs. Radio waves are a form of electromagnetic energy (EM). When this energy
unintentionally affects the operation of an electronic device, it is called Electromagnetic Interference (EMI) or
Radio Frequency Interference (RFI).
WARNING! Radio waves may interfere with the control of power chairs.
FREQUENTLY ASKED QUESTIONS (FAQS)
The following FAQs summarize what you should know about EMI/RFI. Use this information to minimize the risk
that EMI/RFI may affect your power chair.
Where do radio waves come from?
Radio waves are emitted from the antennas of cellular phones, mobile two-way radios (such as walkie-talkies),
radio stations, TV stations, amateur radio (HAM) transmitters, wireless computer links, microwave sources, and
paging transmitters. Radio waves are a form of EMI. Because EMI is more intense closer to the transmitting
antenna (source of emission), the EMI fields from two-way radios are of special concern.
If my power chair is affected by EMI/RFI, what kind of motion should I expect?
This is hard to predict. The effect may depend on a number of factors including:
n Strength of the radio waves
n Construction of the power chair
n Position of the power chair (whether it is on level ground or on a slope)
n Whether or not the power chair is in motion
An affected power chairs movement can be erratic. The chair may move by itself or come to a sudden stop.
Furthermore, it is possible for EMI/RFI to unexpectedly release the brakes on a power chair. Some intense
sources of EMI/RFI can even damage the control system of your Jet 3.
Is there any way to know for sure whether radio waves are responsible for the unintended motion
of my power chair?
Unfortunately, interference from radio wave sources may be difficult to recognize, because the signals from these
sources are invisible and may be intermittent. However, the FDA recommends that you report all incidents of
unintended motion or brake release to the power chair manufacturer and, if possible, note whether there was a
radio wave source nearby at the time of the incident.
Has anyone been hurt from erratic, unintended motion of power chairs?
The FDA has reports of injuries that may have resulted from the uncontrolled motion of power chairs. However,
it is unclear how many of these incidents were actually caused by radio wave interference.
Are all power chairs susceptible to EMI/RFI?
Each make and model differs in its ability to resist electromagnetic interference. That is, each has a particular level
of immunity to interference, measured in volts per meter (V/m). A higher immunity level offers greater protection.
III. EMI/RFI