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TRD0000, TRx Owner’s Manual- Rev. 5.0, January 20, 2005
- 22 -
11.0
Electro-MMagnetic
Interference
Electromagnetic Interference (EMI) From Radio Wave Sources
Power positioning systems may be susceptible to electromagnetic interference (EMI), which is interfering
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 power positioning system to function by itself, or activate in unintended directions. It can also
permanently damage the control system.
The intensity of the interfering EM energy can be measured in volts per meter (V/m). Each power posi-
tioning system 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 radiat-
ed 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.
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 trans-
mitting unit) - examples include: cellular telephones, citizen band (CB) radios,"walkie-talkies", security, fire
and police transceivers and other personal communication devices. NOTE: Some cellular telephones and
similar devices transmit signals while they are "ON", even when they are not being used.
2. Medium range mobile transceivers, such as those used in police cars, fire trucks, ambulances, and taxis.
These usually have the antennae 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, 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 power wheelchair.
Electromagnetic Interference Warning
WARNING! It is very important that you read this information regarding the possible
effects of electromagnetic interference on your TRx power positioning system.
In addition, operation of power positioning systems can create electro-magnetic interfer-
ence, the effect of which cannot be determined. Please make sure to read the associated
warnings in the owner's manual for your power base.
!