File:Core-less induction coils in telephone service (1907) (14569513127).jpg

Identifier: corelessinductio00smit (find matches)
Title: Core-less induction coils in telephone service
Year: 1907 (1900s)
Authors: Smith, Claude E Stewart, Walter M
Subjects: Induction coils Telephone Telephone systems Theses
Publisher:
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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At times there was a sort of buzzi*»g,and the words seemed to occasionally %q run together. We th.oughi.that this was due to the shortness of the line and so we put ina considerable resistance and capacity, A little of the harshnesswas cut out and the sound v/as some clearer. We next removed theiron core from this coil just to see what v/ould be the effect. Theharshness v/as entirely eliminated a id there v/as no trace of theformer buzzing. Such a coil v/ould v/ork very well perhaps , on shortlines, but on comparatively long lines the tra iswission would bepoor, and prove unsatisfactory, because of the xack of the ironcore. I may say that this coreiess coil transmited sound v/hichwas practically the same as that transmited by the large thirty-ty inch coil, which v;iil next be described. After a number of triais using different sizes of wire andvarious number of turnes, v/e decided on an inductio.» coil, theprimary wound with 31 turnes of # 25 copper wire on a 30 inch bicy- !I. If II
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cxe rim giving, a resistance of 8 ohms. The secondary consisted of168 turns of # 36 copper v/ire wound on a 28 inch bicycle rim, giv-ing a resistance of 518 ohms. The current in the primary wab sup-plied by two standard gravity cells in series. When comparing thiscoil v/ith the standard Coil, the core of the standard coil was in-tact. The method of comparison was for one of the operators to starcounting with the standard coil in the circuit, and having countedup to four or five, throw in t^o tost coil, count on up to, say,ten, and throw in the standard again and so on. When compared with the standard coil with the primary and se-condary of the test lying in the same plane, secondary inside theprimary, tno sound transmitcd had more quality. It v/as distinct,and there was no buzzing and harshness. It seemed to resemble moreperfectly the tone and pitch of the human voice, hut was lackingthat intensity of soimd of the standard coil. This lack of inten-sity was perhaps due to the fact thatcorelessinductio00smit

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