File:Induction coils - how to make, use, and repair them including Ruhmkorff, Tesla, and medical coils, Roentgen radiography, wireless telegraphy, and practical information on primary and secondary battery (14754598591).jpg

Identifier: inductioncoilsho00schn (find matches)
Title: Induction coils : how to make, use, and repair them including Ruhmkorff, Tesla, and medical coils, Roentgen radiography, wireless telegraphy, and practical information on primary and secondary battery
Year: 1901 (1900s)
Authors: Schneider, Norman H. (Norman Hugh)
Subjects: Induction coils Radiography X-rays Radiography
Publisher: New York : Spon & Chamberlain London : E. & F.N. Spon
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ireless Telegraphy. 249 relay. A wire is led from one side of thiscoherer up into the air to intercept theHertzian waves, the other side of the cohereris put to earth, or grounded. When awave strikes the air wire it sends a currentthrough the coherer to ground (as before itsent a spark across the air gap), and thiswave acts on the filings in its passagethrough them; in effect, to lower their resist-ance, so that the current is increased throughthe relay circuit and the relay armature isattracted to its magnet. The relay makescontact in the usual manner at the platinumpoints, and in its turn causes the localcircuit, sounder, bell, or pen register torecord the wave (or signal). After eachwave the filings are in such state that torestore them to their former high resistanceit is necessary to give the coherer a smarttap. This is generally accomplished auto-matically by means of an arm extendingfrom the sounder lever, which strikes againstthe coherer each time the sounder armatureis moved.
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Fig. 74. Wireless Telegraphy. 251 Figures 74 and 75 are diagrams of asimple circuit, Fig. 74 being the transmittingapparatus and Fig. 75 the receiving appa-ratus. In Fig. 74 P P and wS vS are the primaryand secondary of a Ruhmkorff coil, D twobrass balls on the discharger, B the battery,K a key, in place of the usual contactbreaker, which is either absent or screweddown; V a wire leading from one arm ofthe discharger up into the air, of a heightvarying with the results desired; G a groundplate in connection with the other dischargerarm. The coil condenser is left out of the dia-gram for sake of clearness; but, of course,is necessary to the operation of the appa-ratus. In Fig. 75, C is the coherer, also calledthe Branly tube, or radio conductor; 6^a telegraph sounder, or electric bell; R arelay; R B and L B the relay battery andlocal battery, respectively; G a ground con-nection; M a resistance, or choke coil, and

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