Motorola VSWR, Service Manual Supplement

Page: 14 / 44

Human exposure to radio frequency energy (PCS1900 only)
5th Feb 99
6
Service Manual Supplement: VSWR Monitor for M-Cell 6
68P02900W86-O
Human exposure to radio frequency energy (PCS1900 only)
Introduction
This equipment is designed to generate and radiate radio frequency (RF) energy. It
should be installed and maintained only by trained technicians. Licensees of the Federal
Communications Commission (FCC) using this equipment are responsible for insuring
that its installation and operation comply with FCC regulations designed to limit human
exposure to RF radiation in accordance with the American National Standards Institute
IEEE Standard C95.1-1991,
IEEE Standard for Safety Levels with Respect to Human
Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz.
Definitions
This standard establishes two sets of maximum permitted exposure limits, one for
controlled environments and another, that allows less exposure, for uncontrolled
environments. These terms are defined by the standard, as follows:
Uncontrolled environment
Uncontrolled environments are locations where there is the exposure of individuals who
have no knowledge or control of their exposure. The exposures may occur in living
quarters or workplaces where there are no expectations that the exposure levels may
exceed those shown for uncontrolled environments in the table of maximum permitted
exposure ceilings.
Controlled environment
Controlled environments are locations where there is exposure that may be incurred by
persons who are aware of the potential for exposure as a concomitant of employment, by
other cognizant persons, or as the incidental result of transient passage through areas
where analysis shows the exposure levels may be above those shown for uncontrolled
environments but do not exceed the values shown for controlled environments in the
table of maximum permitted exposure ceilings.
Maximum
permitted
exposures
The maximum permitted exposures prescribed by the standard are set in terms of
different parameters of effects, depending on the frequency generated by the equipment
in question. At the frequency range of this Personal Communication System equipment,
1930-1970MHz, the maximum permitted exposure levels are set in terms of power
density, whose definition and relationship to electric field and magnetic field strengths are
described by the standard as follows:
Power density (S)
Power per unit area normal to the direction of propagation, usually expressed in units of
watts per square metre (W/m
2
) or, for convenience, units such as milliwatts per square
centimetre (mW/cm
2
). For plane waves, power density, electric field strength (E) and
magnetic field strength (H) are related by the impedance of free space, 377 ohms. In
particular,
S +
E
2
377
+ 377 H 2
where E and H are expressed in units of V/m and A/m, respectively, and S in units of
W/m
2
. Although many survey instruments indicate power density units, the actual
quantities measured are E or E
2
or H or H
2
.