The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 60
to Bells. 45 at A, the result of which is that the hammer passes over to the left handdome. It will be seen that a succession of currents in opposite directionswill cause the hammer to vibrate between the two domes, thus giving aring. Adjustment of the play of the armature is made by moving… … Figure 35. The external appearance of a magneto bell is shown in Figure 35. Itsresistance is now 1,000 , though formerly many of lower resistances, 100 ■*to 500 , were used. The high resistance bells require far less current,and in a large exchange this is an important matter, as the pulling upof…
Telephone · Postal service
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