Like so many pieces of advanced technology, everyone uses a cell phone, but rarely can we explain how it works. If asked to explain, more than likely something about air waves and frequencies will turn up, but typically this just adds to the confusion.
Whether they are used for voice or date transmission, cell phones rely on a network (called a “cell”, hence the name “cell phone”) made of base stations, antennas and electronic equipment. The easiest way to understand cell phone use is considering it an advanced two way radio. When someone speaks into their phone their voice gets converted to radio waves. Next, the radio waves travel until they reach a nearby base station. Then the base station sends the call across the communication network until it reaches its destination—in other words, the person you are calling. Finally, the person receiving the cell phone call has the base station near them translate the air waves (sent from the first station) into a voice message.
Telephone network’s base stations are usually fitted with a microwave antenna. For optimal range they are typically mounted high on a tower or pole. In the early days of car phones each city had one antenna, and as a result, the phone itself required a bigger antenna in order to make a connection up to about seventy kilometers. Another limitation was the limited number of people who could simultaneously use the phone.
One of the keys to understanding the advancements in cell phone technology over the past couple decades is how cell phones seamlessly switch between base stations. One can be in the middle of a conversation with someone and switch back and forth between stations without noticing any interruption in their conversation. When a cell phone conversation goes from one channel to another without a disturbance it is known as a “hand-off”.
Given their ubiquity and their ability to reach anyone across the world at any given moment, it might surprise people to learn that a key part of cell phone technology is actually low power transmitters. This serves two important purposes. By sending out a less powerful signal it means the cells can reuse the same signals which leads to increased connectivity. Secondly, the lower power transmission requires a smaller battery. It’s not hard to see how this has contributed to the ever shrinking cell phone, making it truly portable compared to those of the eighties.
Cell phones are powered by rechargeable batteries. Nickel-metal hybride or lithium ion batteries are the most common battery around. Recently, many companies have switched to lithium polymer batteries because they weigh less and can be found in different shapes. Below the battery is a tiny chip known as a Subscriber Identification Module, or more commonly known by the acronym S.I.M. card. This is essentially a tiny USB card where your phones memory can be stored. Should something happen to your phone, being able to immediately store your old phones contact information is vital!
Hopefully now you can diminish the confusion when someone asks why their cell phone works!