The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 36
ition of the magnet with respect to the diaphragm Double Pole Bell Receiver. 21 D D Is readily adjustable by means of the screw S. The instrumentillustrated is the metal-cased receiver, the shaded portion of the casebeing metal and the black part ebonite, but the receiver specially madefor the Post… … Figure 12. cased receiver was employed. The double pole receiver is certainly oneof the most successful and efficient modifications of the Bell instrument,and it is light and of a convenient shape and size. The Collier-Marr receiver, which has two diaphragms, is more sensitivebut its somewhat…
Telephone · Postal service
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