User Manual

Human Exposure Compliance RF-Orchestra!™ Transmitter Installation and Operation
xxii 6880493G02-C July 2000
At the frequency range of 930–931 MHz and 940–941 MHz for this Personal Communication
System equipment, the maximum permitted exposure levels are set in terms of power density.
Power density definitions and relationships 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 meter (W/m
2
) or, for convenience, units such as
milliwatts per square centimeter (mW/cm
2
). For plane waves, the power density, electric field
strength (E), and magnetic field strength (H) are related by the impedance of free space, in
other words, 377 Ohms. In particular:
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 one of the following: E, E
2
, H, or H
2
.
Within this frequency range, the maximum permitted exposure ceiling for general
population/uncontrolled environments is a power density (mW/cm
2
) that equals f/1500,
where f is the frequency expressed in MHz, and measurements are averaged over a period of
30 minutes. The maximum permitted exposure ceiling for occupational/controlled
environments, also expressed in power density (mW/cm
2)
, is f/300, where measurements are
averaged over 6 minutes. Applying these principles to the minimum and maximum
frequencies for which this equipment is intended to be used yields the maximum permitted
exposure levels:
If you plan to operate the equipment at more than one frequency, compliance should be
assured at the frequency which produces the lowest exposure ceiling (among the frequencies
at which operation will occur).
Licensees must be able to certify to the FCC that their facilities meet the above ceilings.
Whether a given installation meets the maximum permitted exposure ceilings depends, in
part, upon antenna type, antenna placement, and the output power to which this equipment is
Uncontrolled Environment Controlled Environment
930 MHz 941 MHz 930 MHz 941 MHz
Ceiling 0.6203 mW/cm
2
0.627 mW/cm
2
3.101 mW/cm
2
3.135 mW/cm
2
S
=
E
2
= 337 H
___
377