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Earth-return telegraph is the system whereby the return path for the electric current of a telegraph circuit is provided by connection to the earth through an earth electrode. Using earth return saves a great deal of money on installation costs since it halves the amount of wire that is required, with a corresponding saving on the labour ...
Cooke and Wheatstone's five-needle telegraph from 1837 Morse telegraph Hughes telegraph, an early (1855) teleprinter built by Siemens and Halske. Electrical telegraphy is a point-to-point text messaging system, primarily used from the 1840s until the late 20th century.
A relay allows circuits to be switched by electrical equipment: for example, a timer circuit with a relay could switch power at a preset time. For many years relays were the standard method of controlling industrial electronic systems. A number of relays could be used together to carry out complex functions (relay logic). The principle of relay ...
Electrical contacts attached to it closed and completed a secondary circuit. A local battery provided the current for a new pulse through the contacts and onwards along the telegraph line. Davy's relay was the first device to use metallic make-and-break contacts, a great improvement on electrodes dipping into a container of mercury. [5]
The matched termination load and relay coil are matched to an identical setup at the receiving end, to keep the current between the two solenoid coils as even as possible. The other half of the current is sent down the wire to the remote relay (which often switches the remote signal relay) and its termination load.
[1] [2] [3] Chappe used the term "télégraphe" to describe the mechanism he had invented – that is the origin of the English word "telegraph". [4] Lines of relay towers with a semaphore rig at the top were built within line of sight of each other, at separations of 5–20 miles (8–32 km).
The one-needle telegraph proved highly successful on British railways, and 15,000 sets were still in use at the end of the nineteenth century. Some remained in service in the 1930s. [23] The Cooke and Wheatstone telegraph was largely confined to the United Kingdom and the British Empire. However, it was also used in Spain for a time. [24]
Telegraph Sounder. A telegraph sounder is an antique electromechanical device used as a receiver on electrical telegraph lines during the 19th century. It was invented by Alfred Vail after 1850 to replace the previous receiving device, the cumbersome Morse register [1] and was the first practical application of the electromagnet.
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