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REGULATORY INFORMATION
251
SAR levels is typically found in the exhibits associated with the grant.
Once a grant is accessed, the exhibits can be viewed by clicking on
“View Exhibit.” Grants authorized prior to 1998 are not part of the
electronic database but, rather, have been documented in the form of
paper records.
The FCC database does not list phones by model number. However,
consumers may find SAR information from other sources as well.
Some wireless phone manufacturers make SAR information available
on their own Web sites. In addition, some non-government websites
provide SARs for specific models of wireless phones. However, the
FCC has not reviewed these sites and makes no guarantees of their
accuracy. Finally, phones certified by the Cellular Telecommunications
and Internet Association (CTIA) are required to provide SAR
information to consumers in the instructional materials that come
with the phones.
Do hands-free kits for wireless phones reduce risks from
exposure to RF emissions? Since there are no known risks from
exposure to RF emissions from wireless phones, there is no reason
to believe that hands-free kits reduce risks. Hands-free kits can be
used with wireless phones for convenience and comfort. These
systems reduce the absorption of RF energy in the head because the
phone, which is the source of the RF emissions, will not be placed
against the head. On the other hand, if the phone is mounted against
the waist or other part of the body during use, then that part of the
body will absorb more RF energy. Wireless phones marketed in the
U.S. are required to meet safety requirements regardless of whether
they are used against the head or against the body. Either
configuration should result in compliance with the safety limit.
Do wireless phone accessories that claim to shield the head from
RF radiation work? Since there are no known risks from exposure
to RF emissions from wireless phones, there is no reason to believe
that accessories that claim to shield the head from those emissions
reduce risks. Some products that claim to shield the user from RF
absorption use special phone cases, while others involve nothing
more than a metallic accessory attached to the phone. Studies have
shown that these products generally do not work as advertised.
Unlike “hand-free” kits, these so-called “shields” may interfere with
proper operation of the phone. The phone may be forced to boost its
power to compensate, leading to an increase in RF absorption. In
February 2002, the Federal trade Commission (FTC) charged two
companies that sold devices that claimed to protect wireless phone
users from radiation with making false and unsubstantiated claims.
According to FTC, these defendants lacked a reasonable basis to
substantiate their claim.
What are wireless telephone base stations? Fixed antennas used
for wireless telecommunications are referred to as cellular base
stations, cell stations, PCS (“Personal Communications Service”)
stations or telephone transmission towers. These base stations
consist of antennas and electronic equipment. Because the antennas
need to be high in the air, they are often located on towers, poles,
water tanks, or rooftops. Typical heights for freestanding base station
towers are 50-200 feet.
Some base stations use antennas that look like poles, 10 to 15 feet in
length, that are referred to as “omni-directional” antennas. These
types of antennas are usually found in rural areas. In urban and
suburban areas, wireless providers now more commonly use panel
or sector antennas for their base stations. These antennas consist of
rectangular panels, about 1 by 4 feet in dimension. The antennas are
usually arranged in three groups ofthree antennas each. One
antenna in each group is used to transmit signals to wireless phones,
and the other two antennas in each group are used to receive signals
from wireless phones.
At any base station site, the amount of RF energy produced depends
on the number of radio channels (transmitters) per antenna and the
power of each transmitter. Typically, 21 channels per antenna sector
are available. For a typical cell site using sector antennas, each of the
three transmitting antennas could be connected to up to 21
transmitters for a total of 63 transmitters. However, it is unlikely that
all of the transmitters would be transmitting at the same time. When
omni-directional antennas are used, a cellular base station could
theoretically use up to 96 transmitters, but this would be very
unusual, and, once again, it is unlikely that all transmitters would be in
operation simultaneously. Base stations used for PCS
communications generally require fewer transmitters than those
used for cellular radio transmissions, since PCS carriers usually have
a higher density of base station antenna sites.
Are wireless telephone base stations safe? The electromagnetic
RF signals transmitted from base station antennas stations travel
toward the horizon in relatively narrow paths. For example, the
radiation pattern for an antenna array mounted on a tower can be