TELEPHONE SYSTEM OF THE UNITED STATES 



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with one or two telephones is needed, but where an inter-communi- 

 cating system or private branch exchange is not justified, so-called 

 wiring plans are used which provide various arrangements for associ- 

 ating the station equipment with the telephone lines. For the most 

 part the customers' needs are satisfactorily met by one of the ten 

 standard arrangements in general use. A specific example is that of 



Fig. 4 — -Telephone booth provided for public telephone stations. 



two central office lines with two main and two extension stations. 

 Calls to or from either telephone line may be made from any one of 

 the four telephones. Answering at a main station provides privacy 

 by cutting off all the other telephones. 



There are in the United States a considerable number of extension 

 stations. At the present time there are in the Bell System over 1.3 



