Palm 700P User's Guide download pdf (Page 239)

IMPORTANT SAFETY AND LEGAL INFORMATION

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

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Palm 700P User's Guide Page 239

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