The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 518
break jack. When the line is disconnectedat the multiple end the relay spring falls back on the earthedspring, which again gives an earthed path for the currentthrough the lamp and the top contact of jack. The engagedtest is obtained as with the ordinary trunk junctions. Telegraph Order-Wire… … Main -=- EBattery -=- Fig. 460.—Superimposed Call-Wire Telephone Circuit(By permission of the Proprietors of The Electrician) key. This key with a headgear sounder made in the formof a headgear telephone receiver, as shown resting on thewriting desk, is used by a special call-wire operator to…
Telephone
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