Carl Emil Krarup (12 October 1872 – 29/30 December 1909) was a Danish telegraph engineer who is chiefly known for the invention of a kind of loaded cable, eponymously called Krarup cable, which made improvements in the transmission of telephone signals, especially on

submarine cables Submarine cable is any electrical cable that is laid on the seabed, although the term is often extended to encompass cables laid on the bottom of large freshwater bodies of water. Examples include: *Submarine communications cable *Submarine power ...

Career

Krarup was originally a civil engineer. He was in charge of public works in Copenhagen until 1898 when he joined the Danish Telegraph Administration. In 1901 he conducted research at the

University of Würzburg The Julius Maximilian University of Würzburg (also referred to as the University of Würzburg, in German ''Julius-Maximilians-Universität Würzburg'') is a public research university in Würzburg, Germany. The University of Würzburg is one of ...

in Germany on loaded lines. Returning to Denmark he continued the theoretical work at the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in ...

and published a paper in 1902.Huurdeman, p. 321.

Krarup cable

Krarup cable is a method of loading lines to reduce their distortion. All methods of loading add series

inductance Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...

to the cable to try to meet the

Heaviside condition The Heaviside condition, named for Oliver Heaviside (1850–1925), is the condition an electrical transmission line must meet in order for there to be no distortion of a transmitted signal. Also known as the distortionless condition, it can be used ...

for no signal distortion. Krarup cable consists of iron wires wound tightly around the copper conducting cores and it is the iron that is the source of the additional inductance. However, it still does not have sufficient inductance to fully meet the Heaviside condition. Its construction also makes it expensive compared to the previously existing method of adding discrete loading coils at intervals along the cable. Against this, Krarup cable is lighter and easier to lay. The weight of early submarine cables using loading coils could cause excessive stress in the cable if not handled carefully. Additionally, Krarup cable has none of the problems of sealing the joins against seawater which was a major problem with loading coils before modern polymers began to be used. For these reasons, Krarup cable was popular on shorter distances, where the distortion was not so high that loading coils had to be used, until the advent of

permalloy Permalloy is a nickel–iron magnetic alloy, with about 80% nickel and 20% iron content. Invented in 1914 by physicist Gustav Elmen at Bell Telephone Laboratories, it is notable for its very high magnetic permeability, which makes it useful as a ...

cable superseded it.Huurdeman, p. 314. The first cable to be laid with Krarup cable, indeed the first cable to be laid with any kind of continuous loading, was between

Helsingør Helsingør ( , ; sv, Helsingör), classically known in English as Elsinore ( ), is a city in eastern Denmark. Helsingør Municipality had a population of 62,686 on 1 January 2018. Helsingør and Helsingborg in Sweden together form the northern ...

(Denmark) and

Helsingborg Helsingborg (, , , ) is a city and the seat of Helsingborg Municipality, Scania (Skåne), Sweden. It is the second-largest city in Scania (after Malmö) and ninth-largest in Sweden, with a population of 113,816 (2020). Helsingborg is the cent ...

(Sweden) in 1902. This cable was engineered by Krarup himself.

Notes

References

*Huurdeman, AA, ''The worldwide history of telecommunications'', pp. 321–322, Wiley-IEEE, 2003. {{DEFAULTSORT:Krarup, Carl Emil 20th-century Danish inventors Danish engineers 1872 births 1909 deaths