Cyclopedia of Telephony & Telegraphy Vol. 1 - A General Reference Work on Telephony, etc. etc. by Robert Millikan;Samuel McMeen;George Patterson;Kempster Miller;Charles Thom
page 110 of 497 (22%)
page 110 of 497 (22%)
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ends so as to form a horseshoe magnet. At the end opposite the
diaphragm these bars clamp between them a cylindrical piece of iron _2_, so as to complete the magnetic circuit at the end. At the end nearest the diaphragm they clamp between them the ends of the soft iron pole pieces _3-3_, and also a block of composite metal _4_ having a large circular flange _4'_ which serves as a means for supporting the magnet structure within the shell. The screws by means of which the disk _4'_ is clamped to the shouldered seat in the shell do not enter the shell directly, but rather enter screw-threaded brass blocks which are moulded into the structure of the shell. It is seen from this construction that the diaphragm and the pole pieces and the magnet structure itself are all rigidly secured together through the medium of the shell at a point as close as possible to the diaphragm. Between the magnets _1-1_ there is clamped an insulating block _5_, to which are fastened the terminal plates _6_, one on each side of the receiver. These terminal plates are thoroughly insulated from the magnets themselves and from all other metallic parts by means of sheets of fiber, as indicated by the heavy black lines. On these plates _6_ are carried the binding posts for the receiver cord terminals. A long tongue extends from each of the plates _6_ through a hole in the disk _4'_, into the coil chamber of the receiver, at which point the terminal of the magnet winding is secured to it. This tongue is insulated from the disk _4'_, where it passes through it, by means of insulating bushing, as shown. The other terminal of the magnet coils is brought out to the other plate _6_ by means of a similar tongue on the other side. In order that the receiver terminals proper may not be subjected to any strain in case the receiver is dropped and its weight caught on |
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