Communicating with light – fibre optics
Box 2 | Digital communication
Most electronic machines – whether they are using electricity in copper wires or light in optical fibres to communicate – use a digital system of codes to convey information. A few years ago this was not so, but as telecommunications has developed there has been a 'convergence' of the basic technology that makes it all work. These days photocopiers, computers, faxes and many other electronic machines use a similar kind of language to perform their work. You don't need to understand what digital technology is to work a computer or fax machine but, as with most things, knowing a bit about how it works helps you make things happen the way you want them to.
Like much technical jargon, the word 'digital' or 'digit' has been completely changed from its original meaning – which was simply a 'finger'. By holding up three fingers or digits you can show somebody you want three of something, so it also came to mean 'number'. The word got borrowed when clocks with numbers (instead of hands) appeared and got called 'digital clocks'. The word was further stretched when somebody realised the easiest way for computers to talk to each other was in numbers rather than words. So information passing from computer to computer became known as a 'digital transmission' or 'digital signal' – and the word 'digital' came to mean communicating information by numbers.
But why do computers use numbers? Computers may be fast but they are basically pretty dumb. We humans have ten fingers (or digits) and can use them to count up to ten. And we are smart enough to have different names for each of the numbers between one and ten. Also, while we have a ten-based numbering system, computers have trouble coping with something so complicated. Computers only have two 'fingers' (or digits) to count on, so to them it is either one finger or the other. Computers use only the numbers '0' and '1' or 'on' and 'off'. They make up numbers larger than one by using a whole string of zeroes and ones (if you have ever studied a binary or two-based numbering system you will know about this). To give you an example, if you write out the date in ten-based numbers you would get this:
17 November 1998.
But a date in binary computer-talk might look something like this:
101010010010010111100101010100100101010001010101.
When a computer wants to send a message (eg, a word-processing document), it first converts the message to a large number of zeroes and ones and then sends the message down a cable to another computer. The receiving computer reads all the ones and zeroes and reforms them into something we can understand.
Put simply, computers use digital codes to move information about – and like many things to do with the internal workings of computers it can make pretty dull reading until the computer translates it back into 'human talk' for us. The process is similar in almost any electronic machine: fax, phone, mobile phone, tape recorder, CD player, modem – the list goes on. All you have to know is that when you hear people talk about 'digital', they are probably talking about a kind of electronic language that is now used to send almost all messages through the telecommunications system.
Posted May 1997.