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Communicating by Wire
The Telegraph
Introduction
 The
electronic revolution in communications began in the
1800s with the invention and development of the
telegraph.
 Electronic signals were sent over the wires for the first
time to send messages from one place to another.
 Because electronic signals travel over wires at nearly the
speed of light, communication of short messages
became almost instantaneous.
Improvements in
the telegraph led to the
invention and development of the telephone.
In the more than 100 years since the invention of
the telephone, there have been many changes
and improvements in telephone technology and
service.
The telephone remains the cornerstone of
modern electronic communication.
The word
telegraph means to draw or make signs
at a distance.
The first telegraphs were optical telegraphs that
signaled distant locations visually.
During
the French Revolution, Claude Chappe
developed an optical telegraph system that used
high towers located five to six miles apart.
Each tower had wooden arms that could be
swung into different positions to signal messages.
The positions of the arms were read by a
telegraph operator who stood at the top of the
tower and read the signals through a telescope.
Although there were
many early electric
telegraphs proposed or built in the early 1800’s,
the first to have commercial success in the United
States was built by Samuel F. B. Morse.
Morse’ s first telegraph used an electromagnet to
deflect a pencil.
An electromagnet is a coil of wire that makes a
magnetic field (force) when current flows through
the wire.
The pencil made marks on a strip of paper
moving under it.
It became
apparent that it was just as easy for an
operator to interpret the clacking of the
electromagnet as it was to interpret the marks
made on the paper.
The telegraph became an audio rather than a
visual device.
In
1843, Morse got a $30,000 grant from the
United States Congress to build a telegraph
system between Baltimore MD and Washington,
D.C.
In 1844, he finished the system and sent the first
famous message, “What hath God Wrought”
Soon
newspaper reports were using the
telegraph to send news releases.
Railroads used the telegraph to dispatch trains
and set signals.
In 1856, The Western Union Company was
started. In the 10 years that followed, they strung
75,000 miles of telegraph wire.
The telegraph system grew
very fast both in
Europe and the United States.
Thousands of miles of telegraph cable were
strung across the land.
Continents and islands were still isolated by the
water separating them.
While some cables were laid across rivers and
small lakes, the first important body of water to be
spanned was the English Channel, which
separates England from the rest of Europe.
Other larger
bodies of water were then crossed
by cables.
These made larger and larger telegraph
communication networks.
The big challenge was to provide instant
communication across the Atlantic Ocean from
Europe to the United States.
This difficult task took years and years of trying
and several failures before success was
achieved.
 The
first cable to be successfully laid on the ocean bed
from England to North America was finished in 1858 by
Cyrus Field, an American Entrepreneur.
 It stopped working in less than a month but proved that
transatlantic cable was possible.
 In 1866, Cyrus Field laid a new transatlantic cable that
was stronger and worked well.
 His transatlantic cable was the first in a long series of
long distance underwater cables that linked the
continents to provide instant telegraphic communication.