Nokia Sprint PCS Manual page 215

RF signals may affect improperly installed or inadequately
shielded electronic operating systems and/or entertainment
systems in motor vehicles. Check with the manufacturer or
their representative to determine if these systems are
adequately shielded from external RF signals. Also check with
the manufacturer regarding any equipment that has been
added to your vehicle.
Consult the manufacturer of any personal medical devices,
such as pacemakers and hearing aids, to determine if they are
adequately shielded from external RF signals.
Note: Always turn off the phone in health care facilities and request
permission before using the phone near medical equipment.
Turning Off Your Phone Before Flying
Turn off your phone before boarding any aircraft. To prevent
possible interference with aircraft systems, the U.S. Federal
Aviation Administration (FAA) regulations require you to
have permission from a crew member to use your phone
while the plane is on the ground. To prevent any risk of
interference, FCC regulations prohibit using your phone while
the plane is in the air.
Turning Off Your Phone in Dangerous Areas
To avoid interfering with blasting operations, turn your
phone off when in a blasting area or in other areas with signs
indicating two-way radios should be turned off. Construction
crews often use remote-control RF devices to set off
explosives.
Turn your phone off when you're in any area that has a
potentially explosive atmosphere. Although it's rare, your
phone and accessories could generate sparks. Sparks can
cause an explosion or fire, resulting in bodily injury or even
death. These areas are often, but not always, clearly marked.
They include:
Section 4A: Important Safety Information 195