subject: The History Of The Technology Behind The Phone Line [print this page] In the 1870s two inventors both came up with an appliance which was able to transmit analogue signals; i.e. send out speech electrically, this was the first example of the telephone. Elisha Gray and Alexander Graham Bell both rushed to get the idea patented and Bell got their first so is officially credited with being the first inventor of the phone. The breakthrough for Bell came as he was working on improving the telegraph. Both devices work upon the same principles and are wire based systems. The telegraph was capable of transmitting just one signal at a time; Bell realized that it would be possible to transmit simultaneous messages over the same wire. He used his research into music as an example, proving that different pitches could travel along one wire at the same time.
His initial invention the harmonic telegraph demonstrated this possibility. His works then moved on until he realized that he could hear sound through the wires. His famous first words which were spoken across the new telephone were to his assistant Thomas A Watson in the next room. On the first successful experiment with the new device he said Mr Watson, come here, I want to see you.
The first telephone systems were analogue systems. The electronic signals were transmitted via a pair of copper wires which were installed on each line. When the system very first came into being it involved employing operators to connect the calls manually. When you lifted the phone receiver you would at first be put through to an operator who would then ask the number you wanted to connect to. They would then link your line to the desired destination line via a jack and the connection was made. This system could only continue for a limited amount of time as it was costly due to the fact that two copper wires were needed for each line.
This is when digital signals and an automated service came about. Analogue signals are converted to digital signals via a digital convertor. Fibre optic cables allowed hundreds of digital signals to be passed along one line. At the other end of the line the signal is then converted back into analogue to enable it to be heard. Copper wires are still used to transfer the analogue signal to each house at the end of its journey. This combining of the digital and analogue system has allowed the phone network to be financially viable and so its popularity spread.
