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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 ...
In the late nineteenth century, when telephony began to replace telegraphy, it was found that the currents in the earth induced by power systems, electric railways, other telephone and telegraph circuits, and natural sources including lightning caused unacceptable interference to the audio signals, and the two-wire or 'metallic circuit' system ...
The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary among countries, though most follow the recommendations of the International Electrotechnical Commission (IEC). Regulations may identify special cases for earthing in mines, in patient care areas, or ...
In 1838, Steinheil installed a telegraph along the Nuremberg–Fürth railway line, built in 1835 as the first German railroad, which was the first earth-return telegraph put into service. By 1837, William Fothergill Cooke and Charles Wheatstone had co-developed a telegraph system which used a number of needles on a board that could be moved to ...
For example, since there is only one line, winds can't cause lines to clash, removing a source of damage, as well as a source of rural bush fires. Since the bulk of the transmission line has low resistance attachments to earth, excessive ground currents from shorts and geomagnetic storms are more rare than in conventional metallic-return systems.
An isolated ground (IG) (or Functional Earth (FE) in European literature) is a ground connection to a local earth electrode from equipment where the main supply uses a different earthing arrangement, one of the common earthing arrangements used with domestic mains supplies.
An underground power line provides electrical power with underground cables. Compared to overhead power lines, underground lines have lower risk of starting a wildfire and reduce the risk of the electrical supply being interrupted by outages during high winds, thunderstorms or heavy snow or ice storms. An added benefit of undergrounding is the ...
Important examples of these single-wire systems were the Morse telegraph (1837) and the Cooke & Wheatstone single-needle telegraph (1843). In such systems the cost of a return conductor was fully 50 per cent of the cable costs. It was discovered that a return conductor could be replaced with a return path through the Earth using grounding ...