Palm 700P - Manual (Page 239)

I M P O R T A N T S A F E T Y A N D L E G A L I N F O R M A T I O N 233
smartphones 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
smartphones.
Do hands-free kits for wireless smartphones reduce risks from
exposure to RF emissions? Since there are no known risks from
exposure to RF emissions from wireless smartphones, there is no
reason to believe that hands-free kits reduce risks. Hands-free kits
can be used with wireless smartphones for convenience and
comfort. These systems reduce the absorption of RF energy in the
head because the smartphone, which is the source of the RF
emissions, will not be placed against the head. On the other hand, if
the smartphone 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 smartphones 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 smartphone accessories that claim to shield the
head from RF radiation work? Since there are no known risks from
exposure to RF emissions from wireless smartphones, 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 smartphone cases, while others
involve nothing more than a metallic accessory attached to the
smartphone. 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 smartphone.
The smartphone 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 smartphone 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 of three antennas each. One
antenna in each group is used to transmit signals to wireless
smartphones, and the other two antennas in each group are used to
receive signals from wireless smartphones.
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
likened to a thin pancake centered around the antenna system. The
individual pattern for a single array of sector antennas is
wedge-shaped, like a piece of pie. As with all forms of
electromagnetic energy, the power decreases rapidly as one moves
away from the antenna. Therefore, RF exposure on the ground is
much less than exposure very close to the antenna and in the path of
the transmitted radio signal. In fact, ground-level exposure from such