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Communicating in different ways

Illustration of a morse operator

Communicating by current : what can you do with an electrical current?

The most basic form of telecommunications is the electric telegraph - which at its simplest is little more than an electric circuit between a sender and a receiver with a switch included that can make or break the circuit.

The signal you are sending is an electrical current - or a pulse of electromagnetic energy - that makes something happen at the receiver's end of the circuit; swinging a needle, making a buzzer sound or a signal lamp flash.

The simplest circuit, a line wire plus an earth return, gives two basic signal states - on or off. By varying the length of the 'on' signal you can send long or short pulses - the basis of Morse Code.

Domestic telephone user, c1930

Communicating by tone : sound signals

If you can find a way to turn sounds into electrical signals, a whole new range of possibilities opens up.

You can use microphones to turn the sound waves in the human voice into varying electrical currents and then send them down a line - the telephone.

Once you can speak to each other, you have a far more 'instant' form of communication - one that needs no processing, coding or decoding for the user.

When you combine this capability with wireless (radio telephony), you can have telephone conversations between people thousands of miles apart, with no wires in between - or people talking while on the move.

Picture Telegraphy publicity, 1936

Communicating by image : a picture tells a thousand words

Pictures are a very powerful form of communication. A single picture conveys a scene, an instant in time, even a mood, that could require hundreds of words to describe.

The fax - sending still images - provides a way of sending individual pictures. However moving images (television) are arguably even more powerful, enabling people to share a sensation of 'being there'.

This too became possible, by scanning single images one after the other in rapid succession to create the illusion of movement. This trick of the eye relies on the persistence of vision discovered by Peter Roget. It allows us to think that quickly changing images are in fact true movement, which is why successive frames of a film projected in a cinema look 'real' to us.

Moving images were first sent by mechanical scanning, using discs with holes. This was followed by electronic scanning, using a beam in a camera tube. Today, they are being turned into digital code using solid-state sensors - and sent that way.

Videoconferencing

Communicating digitally : what can you do with 1s and 0s

Digital means reducing all kinds of information into sequences of 1s and 0s, called binary code, that can be interpreted and processed by computers and other digital devices.

Everything can be converted into digital form - sounds, music, pictures, words and text. Digital is transforming all the old telecommunications technologies. Telegrams have become e-mails. Telephone conversations have become digitally encoded and digitally switched. Radio and television transmissions are becoming digitally recorded and replayed - transmitted as digital 'bitstreams'.

Digitalisation means that technologies start to overlap - a PC can also be a complete home entertainment and communications centre, for instance. It also means that interactivity and intelligence can be added to everything. You want to see more about an item in the evening news? Just go to a special website and explore. You want your own recording of the soundtrack of a film or television programme? Simply download it there and then.

fun and games

Can you beat our games? Explode equipment to see what's inside, hear the changing sounds of telecommunications, see how telecommunications designs have changed over time or send an e-postacard.

what's on

The UK's first permanent gallery dedicated to the history of information and communication technologies opens in the new Information Age gallery at London’s Science Museum.

audio history

Take a trip down memory lane with extracts of the interviews which have been recorded as part of the Connected Earth oral history programme.

featured story

100 years of automatic switching!
In 1912 the GPO installed Britain's first automatic telephone exchange in Epsom.

Discover the early days of the telephone...