. The practical telephone handbook and guide to the telephonic exchange . portional to the strength of the permanentmagnet, and it is important, therefore, to see that the strengthof the magnets is maintained. Reinforced Receiver Cases.—Receiver cases have recentlybeen introduced which have been rendered practically un-breakable by layers of canvas which have been embedded inthe ebonite before vulcanising. This canvas takes up anyshock and prevents the cracking of the ebonite. Br Traurfs Material.—This material is merely a very highquality of vulcanite. The ear-pieces of receivers are made of
. The practical telephone handbook and guide to the telephonic exchange . portional to the strength of the permanentmagnet, and it is important, therefore, to see that the strengthof the magnets is maintained. Reinforced Receiver Cases.—Receiver cases have recentlybeen introduced which have been rendered practically un-breakable by layers of canvas which have been embedded inthe ebonite before vulcanising. This canvas takes up anyshock and prevents the cracking of the ebonite. Br Traurfs Material.—This material is merely a very highquality of vulcanite. The ear-pieces of receivers are made of it,and as it is very tough and strong it withstands the roughusage to which this part of a receiver is peculiarly liable. CHAPTER V TRANSMITTERS IN PRACTICAL USB As stated in Chapter III., the transmitters used in commonpractice are all variations of some form of Hughes microphone,and they may be roughly divided into three classes—viz.(1) the Button Carbon ; (2) the Pencil Carbon; and (3) theGranulated Carbon. The prototype of the first class is the Blake, of the. Fig. 62 second the Crossley, and of the third the Hunnings,transmitter. Blake Transmitter.—This was invented very soon after themicrophone, and for a number of years was more extensivelyused than any other kind of transmitter. It has now, how 74 TRANSMITTERS IN PRACTICAL USE 75 ever, given place to some form of the more powerful granulartransmitter. When properly made and adjusted it gives avery pure reproduction of the voice, but isnot sufficiently powerful for long-distancework, and possesses the demerit of requir-ing adjustment at times. Fig. 62 showsthe inside of the instrument when open,and Fig. 63 a section through the centreof the transmitter. The chief feature of the instrument wasa small pellet of platinum (attached to theend of a light spring, /) which intervenedbetween an iron diaphragm and a smallround carbon block fixed in a brass socket,p, and supported by another spring, g. Thepressure on the pe
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
