File:Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921) (14569603828).jpg

Identifier: automatictelepho00smit (find matches)
Title: Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems
Year: 1921 (1920s)
Authors: Smith, Arthur Bessey, b. 1875 Campbell, Wilson Lee
Subjects: Telephone
Publisher: New York : McGraw-Hill
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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nd makes switching circuit No. 5. Throwing down any handlein the lower horizontal row of local line keys enables the operator to ringthat particular line. Throwing down either key handle in the lowerhorizontal row of trunk keys holds that particular trunk. Operation.—For example, line No. 5 wishes to be connected with lineNo. 2. The removal of the receiver from the switch-hook of the telephoneof line No. 5 closes circuit which pulls up the incoming visual signal of No.5 line. The operator responds to the signal by throwing the answeringkeys (white) of her telephone and line No. 5 to connect the two togetherthrough any switching circuit which is not busy at the time. Learningthat No. 2 is the line desired she throws the ringing key of that line and,if ringing current is not furnished from the central office, operates thehand generator. She then throws the answering key of line No. 2 intothe switching circuit used to connect her telephone with line No. 5 and 158 A UTOMA TIC TELEPHON Y
Text Appearing After Image:
SUBSCRIBERS STATION EQUIPMENT 159 when the connection is established restores her answering key. Whenthe parties hang up the supervisory signal on the switching circuit willoperate and indicate that the conversation is completed. The operatorthen restores all keys to normal. On an incoming call from the automatic central office the ringingcurrent sent out by the connector switch operates the drop associatedwith the trunk. The operator responds by throwing the answeringkey of her telephone and of the trunk line into a non-busy switchingcircuit. When she does this, the 40-ohm line relay, connected in seriesin one side of the trunk and bridged by a condenser, operates and cutsoff the drop and visual signal associated with the trunk. Learning thelocal number wanted the operator throws the trunk-holding key andrestores the trunk-answering key. This holds the trunk by bridging the500-ohm coil across it and pulls up the trunk supervisory or holdingsignal. The operator is now disconnected fro

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