The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 98
phones.—This, althoughnot much used, is interesting as involving an important principle. It is a kind ofdouble Blake, in whichthe effects produced bythe movement of thediaphragm are doubled.Fig. 64 shows the connec-tions : a a is the dia-phragm and b c two carbonblocks rigidly connectedto it, the… … Fig. 63
Telephone
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