The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 529
cting cord, to-gether form a compound supervisory relay. The lamps lightup when the single coil in the third conductor only is energisedand the feeding current has ceased through the double woundcoil owing to the subscriber having hung up his receiver. Aslong as both single and double coils are… … Fig. 464.—Cord Circuit, Glasgow Central Exchange Most of the other details are on similar lines to those of theWestern Electric Co.s system, as are also the subscribersinstrument and line circuits, so that further description isunnecessary. * W. E. Co.s No. 9 C.B. Switch-Board.—This is a type…
Telephone
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