Hitachi SH-G1000 - Manual (Page 234)

Section 4: Safety Guidelines and Warranty Information
226 4A: Safety
2. 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.
3. 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/cm
2 ) or microwatts (one millionth of a watt) per square
centimeter (µW/cm 2 ).
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).
4. 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