The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 272
rth onkey n. Fig. 258 illustratesthe same circuit in thethrough speaking posi-tion. Supervisory relays is actuated, thus con-necting low - resistancecoil e in parallel with12,000-ohni coil d, andthereby actuating relayB at the A exchange.Kelay o is actuatedthrough cut-off relay p,the right armature… … ^LhwHMI ;;:« A% ._ [€>■
Telephone
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