II.

History

It is now taken for granted in developed nations that by pressing a few buttons people can talk to family, friends, or business associates across the world—and at a readily affordable price. The technology that led to one of the most complex creations of the 20th century—the telephone network—has evolved over the past hundred years or so.

The first electrical means of communication was not the telephone, however, but the telegraph, which allowed messages sent in code (usually Morse Code) to be received and printed at a distant location. The age of commercial telegraphy dawned in 1839 when the British pioneers William Fothergill Cooke and Charles Wheatstone opened their line alongside the main railway route running west from London. A technically simpler system of telegraphy was devised in 1843 by Samuel Morse, and after this the spread of telegraph networks was rapid, with routes spreading across most of the countries of the Old and New Worlds and then beneath the oceans that separated them. By 1930 nearly 650,000 km (400,000 mi) of undersea cables had been laid, linking the economic, political, military, and cultural institutions of the world.

An even greater breakthrough was made in 1876, when Alexander Graham Bell made the first telephone call to his assistant with the words “Mr Watson, come here, I want you”. Bell’s invention sparked a series of innovations, ultimately culminating in today’s information superhighway. Key steps along the way were:

In 1889 Almon Strowger developed an automatic switching system that could set up a telephone call without intervention by a human operator. Strowger’s motivation for this invention was to prevent his calls being diverted to a business competitor by his local operator. The impact of the invention was much wider as it provided the basis for the current telephone network.

In 1901 Guglielmo Marconi demonstrated that radio waves could be used to transmit information over long distances when he sent a radio message across the Atlantic. Radio is still one of the key transmission media today, and is the basis of many mobile services.

In 1947 William Shockley, John Bardeen, and Walter Brattain invented the transistor. This enabled the electronics revolution to take place and provided the basis for a computerized, rather than mechanical, telecommunications network.

In 1965 Charles Kao put forward the theory that information could be carried using optical fibres. These have subsequently been developed to provide a means of carrying huge amounts of information at very high speed. Optical fibres form the backbone of the global transmission network (see Fibre Optics).

The modern telephone network can be viewed as a globally distributed machine that operates as a single resource. Much of it uses interconnected computers. The network that most people use to carry voice traffic can also be used to transfer data in the form of pictures, text, and video images.