Editing Loading coil (section)

===Legal battle===
Heaviside never patented his idea; indeed, he took no commercial advantage of any of his work.<ref>Bray, p. 53</ref> Despite the legal disputes surrounding this invention, it is unquestionable that Campbell was the first to actually construct a telephone circuit using loading coils.<ref>Brittain p. 56</ref> There also can be little doubt that Heaviside was the first to publish and many would dispute Pupin's priority.<ref>Brittain, pp. 36, 48-50<br/>Behrend to Searle, in letter quoted by Brittain, p37<br/>Searle to Behrend, 1931, in letter quoted by Brittain, p37<br/>Nahin, p276</ref>

AT&T fought a legal battle with Pupin over his claim. Pupin was first to patent but Campbell had already conducted practical demonstrations before Pupin had even filed his patent (December 1899).<ref>Pupin, M I, ''Art of Reducing Attenuation of Electrical Waves and Apparatus Therefore'', US patent 0 652 230, filed 14 December 1899, issued 19 June 1900.</ref> Campbell's delay in filing was due to the slow internal machinations of AT&T.<ref>Brittain, p. 44</ref>

However, AT&T foolishly deleted from Campbell's proposed patent application all the tables and graphs detailing the exact value of inductance that would be required before the patent was submitted.<ref>Brittain p. 44-45</ref> Since Pupin's patent contained a (less accurate) formula, AT&T was open to claims of incomplete disclosure. Fearing that there was a risk that the battle would end with the invention being declared unpatentable due to Heaviside's prior publication, they decided to desist from the challenge and buy an option on Pupin's patent for a yearly fee so that AT&T would control both patents. By January 1901 Pupin had been paid $200,000 ($13 million in 2011<ref name=Worth>Samuel H. Williamson, "Seven Ways to Compute the Relative Value of a U.S. Dollar Amount, 1774 to present" (Contemporary Standard of Living measure) ''MeasuringWorth'', April 2013.</ref>) and by 1917, when the AT&T monopoly ended and payments ceased, he had received a total of $455,000 ($25 million in 2011<ref name=Worth/>).<ref>Brittain, pp. 54, 55 (footnote), 57</ref>