Welcome to You Ask Andy

Jeffrey Hopper, age 14, of Great Falls, Mont., for his question:

WHEN WAS THE TELEGRAPH DEVELOPED?

Telegraph is a system of communication employing electrical apparatus to transmit and receive signals in accordance with a code of electrical pulses. Attempts to use phenomena associated with electricity in communication began long before the 19th Century.

The first practical suggestion for construction of an electric telegraph came in 1753 when a British surgeon named Charles Morrison suggested an instrument that would employ electricity sent over wires for a great distance, with the earth completing the circuit between two points. Systems of this type were actually built a few decades later.

But the first instruments for telegraphic transmission were invented in the United States by an American scientest named Samuel Morse in 1837 and in Great Britain in the same year by a British physicist named Sir Charles Wheatstone in collaboration with a British engineer named Sir William Cooke.

Morse is credited with being the inventor of the first practical telegraph system. He used a simple code in which messages were transmitted by electric pulses passing over a single wire.

Morse's apparatus, which sent the first public telegram in 1844, resembled a simple electric switch. It allowed current to pass for a prescribed length of time and then shut it off, ail at the pressure of a finger. The original Morse receiver had an electromagnetically controlled pencil that made marks on paper tape moving over a clockwork operate d cylinder.

Morse found that signals could be transmitted successfully for only about 20 miles so he and his associates developed a relay apparatus that could automatically relay impulses. Telegraph operators also discovered that it was easy to distinguish dots and dashes by sound alone so the Morse recording apparatus was discarded.

Soon several means of sending several messages simultaneously over a single wire were developed.

In quadruplex telegraphy, invented in 1874 by the great American engineer named Thomas Edison, two messages were transmitted in each direction simultaneously. In 1915 multiplex telegraphy came into use, permitting the transmission of eight or more messages simultaneously.

Because of this and the development of teleprinting machines during the mid 1920x, the Morse manual telegraph system of code and key was gradually discontinued for commercial use and replaced by automatic wire and wireless radio wave methods of transmission.

In commercial operations costs have been cut and speed and accuracy of communication increased by the introduction and improvement of automatic sending and receiving equipment. Two basic telegraphic systems developed: the teleprinting system (teletype) and the facsimile reproducing system.

Speed is the keyword for modern telegraph dispatching today. Microwave telegraphy is capable of carrying communications great distances almost instantaneously. Data in various forms can be transmitted rapidly. Recent improvements are expected to permit very high speed transmission of more than 5,000 characters per second, between computers and business machines.

 

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