Following the Path of Discovery
Repeat Famous Experiments and Inventions
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The earliest forms of telegraphy were probably smoke, fire or drum signals. In the late 18th century optical telegraphs were invented by Claude Chappe in France and George Murray in England – the semaphore, based on visible transmission encoded by different positions of pivoted arms located on high towers, but this slow and ineffective system couldn't work at night.
Rapid development of the electrical telegraph was based on Hans Christian Oersted’s discovery in 1819 that a wire carrying a current was able to deflect a magnetized compass needle. The Cooke and Wheatstone five needle telegraph of 1837 utilized this phenomenon. This apparatus, which is generally regarded as the first functional electric telegraph, was widely used in Great Britain for railroad signaling.
The needle telegraph, even after improvement, required two or more lines to form a complete circuit. It was also relatively slow and the design of the transmitting and receiving instruments was complex. Something simple and efficient was needed.
In 1825, British inventor William Sturgeon, exhibited the electromagnet for the first time. Sturgeon displayed its power by lifting nine pounds with a piece of iron wrapped with wires (electromagnet) through which the current of a cell battery was sent.
In 1830, an American inventor, Joseph Henry, demonstrated the potential of Sturgeon's device for long distance communication by sending an electronic current over one mile of wire to activate an electromagnet which caused a bell to strike. Thus the electric telegraph was born.
Samuel F.B. Morse successfully exploited Henry's invention commercially.
Together with his partner Alfred Vail, Morse developed in 1838 the simple operator key, which when depressed completed an electric circuit and sent a signal to a distant receiver which was an electromagnet that moved a marker that embossed a series of dots and dashes (the Morse Code) on a paper roll (patent No.1647).
About 1856 a sounding key was developed that enabled operators to hear the message clicks and write or type it directly down in plain language.
Telegraph systems quickly spread across Europe and the United States. With the growing telegraph traffic many improvements followed. Like the duplex circuit, in Germany, that made it possible for messages to travel simultaneously in opposite directions on the same line. Thomas Edison devised a quadruplex in 1874 that enabled four messages to travel at once. The most revolutionary invention was that of Jean-Maurice-Emile Baudot, his time division multiplex invented in 1872.
Further qualitative improvements were made by Marconi, Tesla, Lodge, Edison, and others by the introduction of the wireless telegraph (radio).
A simple telegraph is a really simple electrical circuit. At the transmission station we have a Morse key which can be a homemade switch from some flexible electricity conducting metal strip like tin or a Radio Shack switch. When pushed down it closes the electrical circuit through the telegraph line and operates a homemade electromagnet or relay at the receiving station (sounder). The electromagnet activates a switch which activates a bulb / LED or buzzer / bell according to the Morse key rhythm (“dash” or “dot”).
Verify that the batteries voltage is compatible with the buzzer / bell / LED / bulb specifications.
You can extend this project and record the received Morse code onto paper tape. You’ll have to adapt your electromagnet to also rotate a paper reel and activate a marker or pen for this end. For the mechanical setting of the paper tape you can use some old mechanical counter or clock mechanism or build it from scratch.
The following links will help you in this effort:
How To Make A Homemade Electric Telegraph! - Instructables
How to Build a Telegraph Sounder and Other Telegraph Projects - David M. MacMillan and Rollande Krandall