4 The Balancing Trick
Before I get on to the actual development of the DIY Telephone Exchange it's worth taking a little detour to take a look at the science between linking two phones so a call can take place. This mechanism is done by running a bi-direction signal over two single wires so a conversation can take place. This is known as duplexing and is covered in more detail below. A more efficient way to do this would be to use four wires, but that would add a vast amount of expense for the telephone operator given the amount of extra cable required. If you like old GPO phones and you have ever wondered how they work, wonder no more. In this beautifully simple explanation the riddle wrapped up in an enigma is revealed. Another fascinating site about telecoms can be found at epanorama . It's one of those places that looks like it hasn't changed since the early 90's but it still has some extremely relevant information. A DAA is a really neat solution to a problem by "de-skilling...