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The Telegraph and Beyond (pg. 2)
Electric Telegraphy
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A
telegraph key used to communicate over wires (often along railroad lines) using morse
code.
photo credit Russ Kleinman
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During the beginnings of
the 19th century a modernized version of telegraphy emerged… the electric telegraph.
It involved the employment of electricity. This type of telegraphy can divide itself into
two groups: wire and wireless telegraphy.
Wire Telegraphy
This branch of telegraphy involves electric impulses that transmitted signals in a wire.
One of the firsts discoveries made was the one of Hans Christian Orsted in 1819. It was
based on electric current causing a magnetic needle or pointer to turn. Another discovery
similar to Hans was later made in 1837. It was known as "Cooke and Wheatstone’s
five needle telegraph", which utilized a panel, which was inscribed with letters and
numbers.
Wireless Telegraphy
Telegraphy systems were improving notably throughout the 20th century. In these systems
wires were substituted for the use of microwave radio links, which carry up to 1,800
channels in a single circuit. This extensive development was due to business and
government demands for machines that were easier to use. As a result, radiotelegraph
companies expanded their bandwidth offerings. These improved developments included:
microwave radio, waveguides, satellites, and lasers.
For international telegraphy, satellite transmissions were employed for their
high-frequency radio bands. Nowadays, some teleprinters can print entire lines
simultaneously at a rate of up to 1,000 per minute. Digital computers are also highly used
for coding and decoding the transmission of signals at very high speeds.
As we can see, modern telegraphy offered society systems of communication with greater
speed, efficiency, and more flexibility than those of the 19th century.
The Invention of the Telegraph
Samuel Morse (seen below) and his partner, Alfred Vail, invented the "operator
key" (like a single typewriter key). By depressing the operator key, a signal would
be sent to a distant receiver. This key projected a series of dots and dashes on a paper
roll. However, in 1856 everything changed.
A sounding key was developed. This apparatus allowed operators to listen to what the key
"said" and typed the messages directly, after 1878. As the spread of telegraph
systems increased, many associations in the United States and Europe, such as the Western
Union Telegraph Company, were establishing (1856).
Later, in Germany, a
duplex circuit was created, which made it possible for messages to travel at the same
time, in opposite directions on the same line; after that, a quadruplex circuit was
invented which permitted four messages to travel at once.
The most revolutionary discovery was Jean-Maurice-Emile Baudot’s "time division
multiplex", in 1872. Her instrument contained a copper ring that was divided into
equal sectors and a brush would travel around it to pick up coded numbers from each
sector. The more sectors an apparatus had, the more messages that could be sent
simultaneously.
"The world was crisscrossed by telegraph lines by the end of the XIX
century…" Between 1924 and 1928, teleprinters (transmitted page form telegrams)
were developed and used for business communications. In 1933, these instruments were
capable of printing only up to 500 characters per minute; by 1964 improved versions
produced up to 900 characters per minute.
Take the telegraphy quiz!
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Pre-electric Telegraphy
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