The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 147
Fig. 136 horizontal metal ring pivoted on a diameter at right anglesto the lever. When the receiver is lifted, a spiral springunder the ring forces up the lever and one side of thering, and two contact points on the far side of the ringare brought into contact with two insulated springs. Thebase of…
Telephone
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