The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 43
y until recently to the exclusion of all others. Class III.—Granular Transmitters. The granular transmitters are instruments in which carbon in granularform is used. The great trouble with transmitters of this class is thatthey become practically useless when the granules become damp andclogged.… … Figure 19. with little carbon granules. The front plate D, held in position by meansof the ring RRi, acts as the diaphragm. The cover carrying the mouth-piece M serves to clamp the diaphragm D in. position. A small fine wiregrid is put across the mouth-piece to arrest moisture. The principle…
Telephone · Postal service
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