How Cell Phones Work
Each day thousands of people in the United States purchase
cellular phones. At that rate it is likely that someone you know
owns a cell phone and uses it on a regular basis. They are such
great gadgets - and there are a ton of cool cell phone
accessories you can buy to make yours stand out from the crowd.
With a cell phone you can talk to almost anyone from just about
anywhere, because approximately 80% of the U.S. has coverage.
Cell phones have come a long way in a relatively short period of
time but have you ever wondered exactly how a cell phone works?
A cell phone is nothing more than a sophisticated radio. A good
way to understand the sophistication of a cell phone is to
compare it to a CB radio. A CB radio is a simplex device. A
simplex device is one in which two people communicate on the
same frequency, so only one person can talk at a time. A cell
phone is a duplex device, so it uses one frequency for talking,
and a second separate frequency for listening. A CB radio has 40
channels. A cell phone can communicate on 1,664 channels. Cell
phones also operate within cells and they can switch cells as
they move around. Cells give cell phones incredible range. A CB
radio can transmit about 5 miles. Someone using a cell phone, on
the other hand, can drive clear across a city and maintain a
conversation the entire time. Cells are what give a cell phone
its incredible range. Cellular phone system technology is
amazing in that a city can be chopped up into small cells that
can allow extensive frequency re-use across a city. Frequency
re-use is what lets millions of people own cell phones without
problems. It works because the carrier chops up an area to about
10 square miles.
Cell phones have low-power transmitters in them. The base
station also transmits at low power. The advantage of low power
transmission is that the power consumption of the cell phone,
which is normally battery-operated, is relatively low. Low power
means small batteries, and this is what has made hand-held
cellular phones possible. Another advantage is that the
transmissions of a base station and the phones within its cell
do not make it very far outside the cell. The same frequencies
can be reused extensively across a city. Cellular phone systems
require a large number of base stations in each city regardless
of the size. The average large city can have hundreds of towers.
In addition to towers, each carrier in each city also runs one
central office called the Mobile Telephone Switching Office
(MTSO). This office handles all of the cellular phone
connections to the land-based phone system and controls all of
the base stations in the region.
Cell phone technology is amazing and improving everyday. It is
hard to imagine life without this little gadget.