Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921)
Smith, Arthur Bessey, b. 1875, Campbell, Wilson Lee · New York : McGraw-Hill · leaf 323
Toll Line Circuit-1 Toll Line Circuit-? … Toll Board Toll Board Fig. 252.—Automatic toll lines (scheme). into the jack, the operator throws the calling device key, she can put thecall through automatically. After dialing the number, the operatorrings with the regular ringing key. This operation holds no matterwhether she is switching toll…
Telephone
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