I-GO Crest CSS, User Manual

PAGE 7

3. EMI

This section provides the user with basic information that describes the problems with 
electromagnetic interference (EMI), known sources of EMI, protective measures to either 
lessen the possibility of exposure or to minimize the degree of exposure, and suggested 
action should unexpected or erratic movement occur.

Attention

It is very important that you read this information regarding the possible  
effects of electromagnetic interference on your Crest CSS power chair.

Attention

Some mobile telephones and similar transmit signal while they are ON, even 
when not being used.

Electromagnetic Interference (EMI) from radio wave sources

Power chairs 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 mobile phones.  
The interference (from radio wave sources) can cause the power chair 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 interfering EM 
energy can be measured in volts per meter (V/m).  Each power chair can resist EMI up 
to 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 radiated EMI.  This power chair model has an immunity level of 20 V/m  
without any accessories. 

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.  However, we believe that by following 
the guidelines listed below your risk to EMI will be minimized.

The sources of radiated EMI can be broadly classified into three types:

1.  Hand-held portable transceivers (transmitter-receivers with the antenna mounted 

directly on the transmitting unit.  Examples include: citizens band (CB) radios, “walkie 
talkie”, security, fire, and police transceivers, mobile telephones and other personal 
communication devices.

2.  Medium-range mobile transceivers, such as those used in police cars, fire  

trucks, ambulances and taxis. These usually have the antenna mounted on  
the outside of the power chair.