Cooke and Wheatstone telegraph
The Cooke and Wheatstone telegraph was an early electrical telegraph system dating from the 1830s invented by English inventor William Fothergill Cooke and English scientist Charles Wheatstone. It was the first telegraph system to be put into commercial service. The receiver consisted of a number of needles which could be moved by electromagnetic coils to point to letters on a board. This feature was liked by early users who were unwilling to learn codes, and employers who did not want to invest in staff training.
Ground (electricity)
Long-distance electromagnetic telegraph systems from 1820 onwards used two or more wires to carry the signal and return currents. It was then discovered, probably by the German scientist Carl August Steinheil in 1836–1837, that the ground could be used as the return path to complete the circuit, making the return wire unnecessary. However, there were problems with this system, exemplified by the transcontinental telegraph line constructed in 1861 by the Western Union Company between St. Joseph, Missouri, and Sacramento, California. During dry weather, the ground connection often developed a high resistance, requiring water to be poured on the ground rod to enable the telegraph to work or phones to ring.