Editing Loading coil (section)

===Permalloy cable===
[[File:Permalloy loaded cable construction.svg|thumb|right|300px|Permalloy cable construction]]
Even though the Krarup cable added inductance to the line, this was insufficient to meet the Heaviside condition. AT&T searched for a better material with higher [[permeability (electromagnetism)|magnetic permeability]]. In 1914, Gustav Elmen discovered [[permalloy]], a magnetic nickel-iron annealed alloy. In c. 1915, [[Oliver E. Buckley]], [[Harold D. Arnold|H. D. Arnold]], and Elmen, all at [[Bell Labs]], greatly improved transmission speeds by suggesting a method of constructing [[submarine communications cable]] using permalloy tape wrapped around the copper conductors.<ref name=Huurd314>Huurdeman, p.314</ref>

The cable was tested in a trial in Bermuda in 1923. The first permalloy cable placed in service connected New York City and [[Horta (Azores)]] in September 1924.<ref name=Huurd314/> Permalloy cable enabled signalling speed on submarine telegraph cables to be increased to 400 words/min at a time when 40 words/min was considered good.<ref>Huurdeman, p. 308</ref><!-- Huurdeman has apparently read 2000 characters per minute as 2000 words per minute --> The first transatlantic cable achieved only two words/min.<ref>May, pp. 947, 950</ref>