WHAT IS THE "CELL" IN CELLULAR COMMUNICATION? Cellular makes it
possible for millions of people to use their mobile phones every
day. The name comes from the way individual cells are organized
into a grid. Each cell is about 10 square miles, and has a base
station consisting of a tower and a small building housing the
radio equipment. Cell phones and base stations use low-power
transmitters with limited ranges, so that the same frequencies
can be reused outside the range. All cell phones have individual
codes used to identify the phone, its owner, and the service
provider. Whenever you turn on your cell phone, it listens for a
system identification code on the control channel -- a special
frequency that the phone and base stations use to communicate
with each other -- to locate the base station in the cell in
which you are standing. If it can't find any such code, it is
out of range. This is what happens when you get a "no service"
message. Your service provider's central switching office keeps
track of your