Palm Treo 650, Руководство пользователя

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304 Section 5A: Safety
Consumer Information on Wireless Phones
(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 (RF) energy 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).