The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 80
is connected to the fourth terminal, and the body of the instrument towhich the armature is attached forms the other terminal. The connec-tions are made by brass screws, which not only hold the instrument inposition, but at the same time fit into pieces of brass which are, behindthe switch,… … which by induction is made north, to the left. At the same time thearmature is deflected on to the left hand contact point. Both ends ofthe armature are made into south poles by induction from the lowermagnet; thus the right hand side is attracted and the left hand side isrepelled, so closing the…
Telephone · Postal service
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