Agenda - 10-01-1996 - 9a - Laserfiche WebLink

Browse Search

JULES COHEN & ASSOCIATES, P.C. 9 CONSULTING ENGINEIMS ` WASHINGTON, D.C. 20036 ' Engineering Statement Page 3 Carrboro, North Carolina where f is frequency in megahertz and S is power density in milliwatts per square centimeter (mWJcm'-). Given this relationship, the most restrictive exposure guide level would occur at 869 MHz, the lowest possible operating frequency for cellular base stations. Applying this frequency to the formula yields a protection guide level of 2.9 mW/cmz. The revised standard, C95.1-1992, also specifies maximum exposure in terms of a frequency-dependent maximum level, but, instead of a protection guide, this level is referred to as a maximum permissible exposure (MPE) level. The new standard also categorizes exposure environments as controlled or uncontrolled. The 1982 standard did not distinguish between exposure environments. Under C95.1-1992, 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 arras where analysis shows the exposure levels may be above the MPEs for uncontrolled environments but less than the MPEs for controlled environments. The MPE for controlled environments under the 1992 standard for emissions in the 300 to 3000 MHz frequency range is the same as the 1982 protection guide level and therefore may be calculated using the formula given above. The averaging time for controlled environment exposures is also 0.1 hour as with the 1982 standard. Thus, in this case, the MPE for controlled environments would be the same as the protection guide level, 2.9 mW/cm=. The base of the KNKA293 tower, which is enclosed by a fence, is an example of a controlled environment. Locations inside the KNKA293 equipment shehw also are examples of a controlled environment.