Like so much of our modern infrastructure, the phone for many is just another bit of technical wizardry, the details of which are so far removed from our daily lives. However, when we look inside the phone, we actually find some extremely familiar technologies working in synergy to make this marvel of long distance communications possible.
Let's take a look inside the phone and examine some of the basic principles which make it function.
The Speaker, The Microphone And The Magic Of The Membrane
The basis of all audio equipment is the speaker, which produces sound by vibrating a membrane. The membrane (or “diaphragm”) is mounted to a magnet, which responds to electrical signals with motion, resulting in the sound produced by the membrane.
As fascinating as this mechanism is, we won't delve into it too much. But while we're on the topic of membranes, it is worth noting that the microphone works essentially as a speaker in reverse (in fact, you can actually use a speaker as a rudimentary microphone!) Whereas a speaker uses a membrane to move a magnet to produce sound, a microphone uses a membrane to pick up sounds and turn them into electrical signals which can be reproduced by the speaker.
From Here To There
The basic principles outlined above are the fundamental basis of a phones operation. The phone itself is simply a handset containing a speaker for the earpiece and a microphone for the mouth piece. When someone on one end of the phone speaks into the microphone, the sound vibrates the membrane and is translated into electrical signals by the magnet. This signal then crosses through the telephone system and is reproduced by as sound by the speaker on the other end of the line.
In the earliest days of the telephones history, it really was that simple: long copper wires connected speaker to microphone, and telecommunications was born. The modern telecommunications infrastructure is far more complicated, however, and is comprised of a huge amount of technology which makes up the Public Switched Telephone Network (PSTN.)
A (Very) Brief Look At the PSTN
The PSTN is a massive network of telephone lines, mobile phone networks, fibre optic cables, satellite communications and just about every other form of electronic communication. The entire system is connected via switch boards generously distributed across the globe, and the result is the ability to place a call from any one point in the world to just about any other.
Each phone is assigned a unique code to keep track of it (your phone number) and can access any other phone by inputting the proper number. In travelling through the PSTN, a phone signal might find itself converted into all different sorts of electrical signals, radio signals, make its way through digital processing and much more. While a complicated process, it is, in essence and in result, the same as the highly simplified model of early phone systems we presented above.
How do mobile phones and cordless phones differ?
Both mobiles and cordless phones achieve their wireless capabilities by communicating using radio signals. In the case of a cordless phone, the regular phone signal received from a land line wall jack is converted into radio signals by a transceiver (the base of the phone) and then converted back into electrical signals by the phones handset, before finally being converted into sound by the speaker. Mobile phones have effectively the same process.