Brief History of the Telephone System

First of all it may be useful for a quick description of today's telephone system; currently most people have a telephone connected to a telephone exchange over a length of (usually) copper wire. When you dial on the telephone signals are sent down the wire to the exchange, and the exchange, based on the digits you dial sets up a connection in the phone network between you and the phone you are calling. A signal is sent to the phone you are calling to make it ring, and when it is answered all the voice 'signal' is transmitted down the wires and along the connection through the phone network and the voice may be heard at either end.

This telephone has been around for around 100 years and the main changes over the year have been in the telephone exchanges. Originally manual operators would setup the connection in the telephone network using socket boards; they would basically re-wire the telephone network when someone wanted to make a call. Things moved on with introduction of automatic exchanges – these were very large machines that would pickup the signals dialed on your phone and move connections around directly based on the digits dialed. This allowed many more telephones to be connected to the network and reduced the number of people required to run the telephone system.

The next major change was the introduction of digital exchanges; most modern telephone networks today are digital. In the digital exchange world computers setup the connections based on the digits dialed.

The actual technology the composes the telephone network has also changed dramatically. Originally the telephone network was made up of thousands of copper wires bundled together on telegraph poles connecting telephone exchanges and telephones in peoples houses. Digital exchanges allowed several conversations to be placed on a single copper wire by mixing conversations at one end of the wire and separating them at the other. Fiber optic links vastly increased the capacity of the telephone network by allowing many more conversations to be placed on a cable, and increasing the distance the signal would travel on a cable. In fiber optic systems the telephone signal is converted into light pulses instead of electrical pulses. Radio, microwave and satellite communications are in common use for transmitting telephone signals too.