The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 244
and dashes, whilst the connections spoken through when twolines are connected are drawn in thick continuous lines. In addition to the apparatus shown in Fig. 240, there isshown a pilot relay and lamp, a subscribers service register,and the connections on the distributing frame. Pilot Relay.—This is… … 220 PRACTICAL TELEPHONE HANDBOOK ever a call is made on any one of these lines the pilot relay isoperated, and causes a specially large lamp, called the pilotlamp, to glow. Being placed in a conspicuous position onthe front of the switch-board, it attracts the operators atten-tion, and denotes the…
Telephone
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