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in volts per meter (V/m). Each powered wheelchair can resist EMI up to a certain intensity, or
“immunity level.” The higher the immunity level is, the greater the protection against EMI. At this
time, current technology is capable of achieving at least a 20V/m immunity level, which would pro-
vide useful protection from the more common sources of radiated EMI.
· WARNING Although your power wheelchair has been tested to the
current standard of 20V/m, care should be taken to avoid
electromagnetic sources.
The 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 com-
munication devices.
· CAUTION 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, ambulanc-
es, 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, mobile devices, laptop computers, AM/FM
radios, TV sets, CD players, cassette players, and small appliances, such as electric shavers and hair dryers, are
currently unlikely to cause problems to your power wheelchair.
EMI radiations from hand-held radio sources (transceivers) are of special concern because
they can be brought close to the power wheelchair’s control system. As the transceiver nears the
control system, EMI energy rapidly becomes more intense. This can be unintentional if someone
is not aware of the hazard. Please observe the warnings listed below to prevent possible interfer-
ence with the control system of the power wheelchair:
Note: Adding accessories and components or modifying the unit may change the susceptibility to EMI.