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ELECTROMAGNETIC INTERFERENCE
RADIO WAVE SOURCES MAY AFFECT POWERED MOBILE VEHICLE CONTROL.
Electromagnetic Interference (EMI) From Radio Wave Sources
Power-operated vehicles (POV) 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 POV to release its brakes, move by itself, or move in unintended
directions. It can also permanently damage the POV’s control system.
Three Main Sources of Radiated 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. Three broad classifications of EMI sources are
listed below.
• Handheld portable transceivers (transmitters-receivers) with antenna mounted directly on the transmitting unit. Examples
include: citizens band (CB) radios, “walkie talkie,” security, fire and police transceivers, cellular telephones and other personal
communication devices. Some of these devices transmit signals while they are on, even when not being used.
• Medium-range mobile transceivers, such as those used in police cars, fire trucks, ambulances and taxis. These devices usually
have the antenna mounted on the outside of the vehicle.
• Long-range transmitters and transceivers, such as commercial broadcast transmitters (radio and TV broadcast antenna towers)
and amateur (HAM) radios.
POV EMI Warnings
Because electromagnetic energy rapidly becomes more intense as one moves closer to the source, the electromagnetic fields
from handheld radio wave sources (transceivers) are of special concern. It is possible to unintentionally bring high levels of
electromagnetic energy very close to the POV’s control system while using these devices. This can affect POV movement and braking.
The warnings listed below are recommended to prevent possible interference with the control system of the POV, which could result
in serious injury.
• DO NOT operate or turn on handheld personal communication devices, such as Citizens Band (CB) radios and cellular phones
while the vehicle is turned on.
• Avoid using your POV near transmitters such as radio stations, TV stations and alarm systems.
• If unintended movement or brake release occurs, turn the vehicle off as soon as it is safe.
• Be aware that adding accessories or components or modifying the vehicle may make it more susceptible to interference from
radio wave sources. There is no easy way to evaluate their effect on the overall immunity of the vehicle.
• Report all incidents of unintended movement or brake release to the mobile vehicle manufacturer, and note whether there is a
source of EMI nearby.
• Vehicle may disturb the operation of devices in its environment which emit EM fields.
EMI Immunity
The intensity of the interfering EM energy can be measured in volts per meter (V/m). Each POV can resist EMI up to a certain intensity.
This is called its “immunity level.” The higher the immunity level, the greater the protection.
• 20 volts per meter (V/M) is a generally achievable and useful immunity level against EMI (as of May 1994). The higher the level,
the greater the protection.
• The immunity level of this product is not known.
