Identifier: belltelephonemag09amerrich (find matches)
Title: Bell telephone magazine
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept
Subjects: Telephone
Publisher: (New York, American Telephone and Telegraph Co., etc.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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fall back, and then closed the circuit through heavycalling battery B-l, operating tap bell R-D. The operatorthen shifted plug P-d from the right-hand to the left-hand hole,disconnecting subscriber Z)s central office burglar alarm circuitand connecting the operators telephone, T, to subscriber Z)sline. When his bell rang, subscriber D moved his substationswitch from the right-hand to the left-hand contact, thus dis-connecting his substation burglar alarm circuit from his lineand connecting in his telephone, T-D. The operator, after notifying subscriber D that subscriber Bwished to talk with him, removed plug P-d from the left-handhole, moved switch 5 to its right-hand contact, and insertedplug Q, at the end of cord C, in hole H-d. This placed thetelephones of subscriber B, the operator and subscriber D all inone circuit (Fig. 4). The operator could thus determine, bylistening in, when the conversation was finished. When thisoccurred, the operator withdrew plug Q from hole H-d, re- 209
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210 THE FIRST TELEPHONE SWITCHBOARD placed plugs P-b and P-d in the right-hand holes of the centraloffice plug and block switches, and moved switch 5 to its left-hand contact. When subscribers B and D had moved theirsubstation switches to the right-hand contacts, the operatorrestored the shutters of annunciators A-b and A-d (the latterhaving fallen when its galvanometer circuit was opened), andclosed switch W. The apparatus at the central office and sub-stations was then in readiness for another call to be made. G. K. Thompson,R. B. Hill. Note: The authors wish to express their indebtedness to Mr.W. L. Richards, Consulting Historian of the Bell TelephoneLaboratories, for his assistance in the preparation of this arti-cle. 211 Worlds Telephone Statistics January 1, 1929 ACCORDING to the latest annual survey of the worldstelephones which was recently completed by the ChiefStatisticians Division of the American Telephone and Tele-graph Company, there were 32,712,284 telephones in the wor

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