Palm 680 - Manual (Page 258)

R E G U L A T O R Y I N F O R M A T I O N 252
(The following information comes from a consumer information
Website jointly sponsored by the U.S. Food and Drug Administration
(FDA) and the Federal Communications Commission (FCC), entitled
“Cell Phone Facts: Consumer Information on Wireless Phones.” The
information reproduced herein is dated July 29, 2003. For further
updates, please visit the Website:
http://www.fda.gov/cellphones/qa.html.)
What is radiofrequency energy (RF)? Radiofrequency energy (RF)
is another name for radio waves. It is one form of electromagnetic
energy that makes up the electromagnetic spectrum. Some of the
other forms of energy in the electromagnetic spectrum are gamma
rays, x-rays and light. Electromagnetic energy (or electromagnetic
radiation) consists of waves of electric and magnetic energy moving
together (radiating) through space. The area where these waves are
found is called an electromagnetic field.
Radio waves are created due to the movement of electrical charges in
antennas. As they are created, these waves radiate away from the
antenna. All electromagnetic waves travel at the speed of light. The
major differences between the different types of waves are the
distances covered by one cycle of the wave and the number of waves
that pass a certain point during a set time period. The wavelength is
the distance covered by one cycle of a wave. The frequency is the
number of waves passing a given point in one second. For any
electromagnetic wave, the wavelength multiplied by the frequency
equals the speed of light. The frequency of an RF signal is usually
expressed in units called hertz (Hz). One Hz equals one wave per
second. One kilohertz (kHz) equals one thousand waves per second,
one megahertz (MHz) equals one million waves per second, and one
gigahertz (GHz) equals one billion waves per second.
RF energy includes waves with frequencies ranging from about 3000
waves per second (3 kHz) to 300 billion waves per second (300 GHz).
Microwaves are a subset of radio waves that have frequencies
ranging from around 300 million waves per second (300 MHz) to
three billion waves per second (3 GHz).
How is radiofrequency energy used? Probably the most
important use of RF energy is for telecommunications. Radio and TV
broadcasting, wireless phones, pagers, cordless phones, police and
fire department radios, point-to-point links and satellite
communications all rely on RF energy.
Other uses of RF energy include microwave ovens, radar, industrial
heaters and sealers, and medical treatments. RF energy, especially at
microwave frequencies, can heat water. Since most food has a high
water content, microwaves can cook food quickly. Radar relies on RF
energy to track cars and airplanes as well as for military applications.
Industrial heaters and sealers use RF energy to mold plastic
materials, glue wood products, seal leather items such as shoes and
pocketbooks, and process food. Medical uses of RF energy include
pacemaker monitoring and programming.
How is radiofrequency radiation measured? RF waves and RF
fields have both electrical and magnetic components. It is often
convenient to express the strength of the RF field in terms of each
component. For example, the unit “volts per meter” (V/m) is used to
measure the electric field strength, and the unit “amperes per
meter” (A/m) is used to express the magnetic field strength. Another
common way to characterize an RF field is by means of the power
density. Power density is defined as power per unit area. For
example, power density can be expressed in terms of milliwatts (one
thousandth of a watt) per square centimeter (mW/cm2) or microwatts
(one millionth of a watt) per square centimeter (µW/cm2).
The quantity used to measure how much RF energy is actually
absorbed by the body is called the Specific Absorption Rate or SAR.
The SAR is a measure of the rate of absorption of RF energy. It is
usually expressed in units of watts per kilogram (W/kg) or milliwatts
per gram (mW/g).
What biological effects can be caused by RF
energy? The biological effects of radiofrequency energy should not
be confused with the effects from other types of electromagnetic
energy.
Very high levels of electromagnetic energy, such as is found in X-rays
and gamma rays, can ionize biological tissues. Ionization is a process
where electrons are stripped away from their normal locations in
atoms and molecules. It can permanently damage biological tissues
including DNA, the genetic material. Ionization only occurs with very
high levels of electromagnetic energy such as X-rays and gamma
rays. Often the term radiation is used when discussing ionizing
radiation (such as that associated with nuclear power plants).