Millions of people around the world use cellular phones. These gadgets, sometimes no bigger than a pack of gum, provide an incredible array of functions and new ones are being added at a breakneck pace.

Depending on the cellular phone model, you can store contact information, keep track of appointments, send or receive e-mail, get information from the World Wide Web, play simple games and even integrate other devices such as PDAs, MP3 players and GPS receivers.

But have you ever wondered how a cellular phone works?

One of the most interesting things about a cellular phone is that it is actually a radio — an extremely sophisticated radio, but a radio nonetheless.

We have to go back in time to the invention of the telephone by Alexander Graham Bell in 1876.

Wireless communication can trace its roots back to the invention of the radio by Nikolai Tesla in the 1880s and presented formerly in 1894 by a young Italian named Guglielmo Marconi.

It was only natural that these two technologies would eventually be combined and in 1973, Martin Cooper invented the first cellular phone.

It weighed a whopping two pounds and because they were so big and expensive to make, the first phones were only used by the military and businesses.

But ten years later they were smaller and much less expensive, so they were more available to the general public.

A good way to understand the sophistication of a cellular phone is to compare it to a CB radio, or a walkie-talkie.

A CB radio is a simplex device. That means: two people communicating on a CB radio use the same frequency so only one person can talk at a time, while a cellular phone is a duplex device, which means it uses one frequency for talking and a second, separate frequency for listening.

While a CB radio has 40 channels, a cellular phone can communicate on 1,664 channels.

Cell phones also operate within cells and they can switch cells as they move around and it’s these cells that give cellular phones incredible range. While a walkie-talkie can transmit perhaps a mile, a CB radio, because it has much higher power, can transmit perhaps five miles.

But someone using a cellular phone on the other hand, can drive clear across the Island and maintain a conversation the entire time. It is these cells that give your cellular phone its incredible range.

Just when you thought you understood the basics, along comes digital cellular phones.

If you go back a few years, cellular phones used to be analogue, while the newer systems, or Global Systems for Mobile communications, are digital.

The major difference is how the audio signals, or your voice, is transmitted between the phone and the base station (tower).

Analogue and digital refer to this transmission mechanism and to better understand it you have to think of it as audio cassettes versus CDs. While audio cassettes are analogue, CDs are digital.

In either system, the audio at the microphone always starts out as a voltage level that varies continuously over time. High frequencies (high pitch) cause rapid changes and low frequencies cause slow changes.

With analogue systems, <$>the audio is modulated directly onto a carrier. This is very much like, if not identical to FM radio where the audio signal, or music, is translated to the RF signal.

With digital systems, the audio is converted to digitised samples at about 8,000 samples per second or so. The digital samples are numbers that represent the time-varying voltage level at specific points in time.

These samples, or numbers, are now transmitted as ones and zeros and on the other end are converted back to voltage levels and “smoothed out” so that you get about the same audio signal.

With analogue transmissions, interference that affects the transmitted signal gets translated directly into the recovered signal, so there is no “check” that the signal makes sense.

The great thing about digital is that the ones and zeros can not be easily confused or distorted during transmission, plus extra data is typically included in the transmission to help detect and correct any errors.