Scientific evidences stating Meuccis priority on Bell   Antisidetone circuit  Meucci began investigating topics related with the telephone system in  as shown by a drawing of the same year reproduced below httpwwwchezbasilioitimmaginicorradidrwgif  This drawing formed the basis for Meuccis caveat of  but as Meuccis lawyer did not file it with the caveat it was later notarized by Meucci himself in his affidavit of  October The drawing shows a twoway simultaneous telephone conversation with a complete separation between the two directions of transmission indicated by arrows This contrivance is aimed to counteract the socalled sidetone effect that is the hearing of the echo of the speakers own voice as well as any background noise in his own receiver  This layout is known today as a fourwire circuit With it Meucci anticipated any other inventor as proved by the following  No mention of sidetone effects nor measures to counteract it are found in Bells patents nor in Grays caveat both of  In the first Bells subscriber lines the four initially two instruments were simply put in series on the same line The first antisidetone AST circuits were introduced by the Bell people in the s particularly by George A Campbell with his nine patents of  many decades after Meuccis solution was shown in this drawing and over thirty years after the same drawing was notarized   Inductive loading  The drawing reproduced above httpwwwchezbasilioitimmaginilemmidrwgif is taken from a note jotted down by Meucci in his Laboratory notebook on  September  and reported in an affidavit by M Lemmi of  September  containing the English translation of said notebook see also my paper on Antenna It can be seen that diagrams No  and No  differ from No  in the insertion midway along the longdistance line of an inductor with either a horseshoe or bar iron core In diagram No  the inductor is split into two parts inserted at both ends of the line In his notes Meucci pointed out that in this way he could get rid of the battery and that by splitting the inductor he obtained better results This technique is known today as the inductive loading of long distance telephone lines allowing to increase the distance andor the quality of speech The proof that Meucci came first can be drawn from the following events occurred many years after Meuccis discovery or its notarization  In JuneJuly  Oliver Heaviside and Alfred Vaschy predicted on the basis of mathematical calculations that telephone signals could be transmitted without distortion by increasing the lines selfinduction On  June  M I Pupin obtained the first two patents for said technique The Bell Telephone Co acquired both patents and later on applied them in its lines  Means to counteract the skin effect  Because of the increased bandwidth of the telephone with respect to the telegraph telephone lines were subjected to increased attenuation due to the socalled skin effect In two notes of  in his Laboratory notebook notarized in Lemmis affidavit of  Meucci suggested to treat the surface of the copper conductor in various ways basically with graphite to increase its surface conductivity Moreover in his caveat of  Meucci stated I believe it preferable to have the wire of larger area than that ordinarily employed in the electric telegraph Another note in his notebook dated  August  reads To be adopted for having long distance bundles of copper wire insulated with cotton or any other kind of wrapper by this means I have obtained a distance of about one mile For this bundle of copper wires Meucci filed a US patent application Wire for Electrical Purposes on  July   That Meucci was first in said techniques is proven by the following facts  Skin effect in telephone lines was neglected by all inventors till  when it began to be investigated by David E Hughes and Oliver Heaviside Following their studies and the development of hard drawn copper the Bell Telephone Co decided to use copper in place of steel beginning from the BostonNew York line which was inaugurated on  March    Call signaling  Meucci adopted a telegraphic call signaling simply effected by a Morse key attached to each end of the line momentarily shortcircuiting the local transmitter In this way strong pulses of current were sent along the line and the distant receiver would emit intermittent ticks much louder than the ordinary speech In his caveat of  Meucci gave a detailed description of his call signaling consistent w