The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 173
close the number painted on a. Fig. 162 shows the dropin this position. The shutter is restored by the passage of a current ofsufficient strength through the coil r. This causes the at-traction of a, allowing p to fall into the vertical position.a cannot again fall forward as long as the current is…
Telephone
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