The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 179
Fig. 173.—Scale £ Fig. 172.—Scale £ switch-boards. This jack differs in con-struction from the forms described, thesprings all being made to bear on one sideof the plug. The bush connection spring is used to serveas a stop. The advantages of this mode of constructionare that the plug is pressed…
Telephone
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