Secondary Resource Sheets
Cables for communication
Telecommunications has used cables for over 150 years, and today the
globe is spanned by millions of miles of them. The Connected Earth
exhibition at Amberley Working Museum tells the story of the amazing
power of communication by cable – here is a taster.
Copper cables – wondrous wire
Underground cables are the ‘veins and arteries’ of the telecomms
network. Since the early days of the telegraph, most communications
wires have been made of copper because it conducts electricity so well.
Amberley cable display
Copper cable facts:
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When the first telegraphs were made, electric wire could not be bought so the inventors had to make it.
Some early cables were made with wires set in wood and sealed with pitch (a substance made from tar for
waterproofing).
The first cross-channel cable was laid in 1850. It worked for one day!
The first transatlantic cables were insulated with a type of rubber called Gutta Percha.
A telephone call requires two wires, and some cables have thousands of wires to carry more calls.
Some old copper cables have lasted for 80 years.
Today, copper wires carry digital signals: this means data such as computer files and video as well as voice.
Fibre optics – light work
A fibre optic cable network is like a mirrored tube thousands of miles long. Each fibre optic carries messages
sent as light pulses rather than electrical signals. The core of a fibre optic is a strand of silica glass about the
thickness of a human hair.
Fibre optic facts
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Fibre optic
cables
A single strand optical fibre can carry thousands of phone calls
simultaneously.
Electrical communications signals are converted into light pulses,
billions of times a second, and transmitted by light from lasers or
photo-diodes.
Fibre optics have been used in the UK since 1980.
The glass in an optical fibre is so pure that if you made a sheet of it
15km thick, you would be able to see through it as if you were looking
through an ordinary window pane.
Today, there are thousands of miles of fibre optic cables spanning the
globe’s oceans and continents, carrying huge amounts of Internet
traffic, phone calls and other data.
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Secondary Resource Sheets
Electromagnet mania
The electromagnet was a great invention – in fact, very few of the
electric devices in your home, such as phone, TV, CD/DVD player or
computer would work without them. Electromagnets have also played a
hugely important role in the history and development of
communications. In the Connected Earth exhibition at Amberley
Working Museum, you can see and try out telecomms devices, old and
new, nearly all of which have electromagnets hidden inside.
The telegraph
Bell display at Amberley
In the late 1830s in Britain, scientist–inventors Charles Wheatstone and William Cooke made a great
breakthrough with their needle telegraph. They were able to send electric currents along miles of wire to a
simple coil; this basic electromagnet caused a small needle to move, which made the signal visible. Long
distance communication was a reality. At Amberley, you can see some needle telegraph equipment, and also
send a message yourself, using a much later version of the telegraph.
The telephone
Phones use electromagnets in the speaker (receiver). The story of the early telephone is really the story of
inventors such as Alexander Graham Bell and Thomas Edison working on these two devices to perfect the
telephone. At Amberley, there is a fantastic display of phones through the ages, including some you can
use yourself.
Bells
In the days before ringtones, telephones had bells. These, and most other electric bells, were worked by
simple electromagnets. There is a fun display of large and small telephone bells to test in the Connected
Earth building.
Telephone exchanges
Pre-digital telephone exchanges contained switches for connecting calls.
The machinery in these places used vast numbers of electromagnets to
work relays and other types of switching mechanisms. You can see some
of these in action at Amberley too.
More recent technology
An electromagnet
The electromagnet – basically just a coil of wire wrapped around a
piece of metal – is still found in a wide range of modern telecomms
equipment. They are inside fax machines, PC monitors, radios, hard
drives, speakers, mobiles and many other devices. Has any other
invention played such an important role in communication?
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