The practical telephone handbook and guide to the telephonic exchange (1906) (14776030283)

Identifier: practicaltelepho00pool (find matches)

Title: The practical telephone handbook and guide to the telephonic exchange

Year: 1906 (1900s)

Authors: Poole, Joseph

Subjects: Telephone

Publisher: New York, Macmillan Co.

Contributing Library: Northeastern University, Snell Library

Digitizing Sponsor: Boston Library Consortium Member Libraries

Text Appearing Before Image:

Fig. 201 used. As with the single-cord board, a telephone set pro-vided with a single 2-point plug is used for operating. Another plan of working double-cord boards is to join thedrop coils to the two outer springs of the jack, and use a singledouble-strand cord, with a 2-point plug joined to each end forconnection. When lines are connected, both drops are then SMALL SWITCH-BOARDS 175 left in shunt to the lines, and both fall when the clearingring is given. In such an arrangement tubular drops of highresistance (1000 ohms) must be used. Special Exchange Working.—When the double-cord boardsare needed principally for exchange working, the exchange

Text Appearing After Image:

r jpa/- y.-« □ s> The. earth,on thecentreopservice instrument bellcous when the hook isdown, 15 only necessarywith automatic clearing Fig 202 junction lines are furnished with special apparatus, and theworking is modified. Two jacks (Fig. 202) are fitted for theexchange line, the upper one called the connecting-jack andthe one below the service-jack. The connecting-jack is a4 or 5-point break-jack, to the outer springs of which theexchange line is connected. The service-jack is a 7-point 176 PRACTICAL TELEPHONE HANDBOOK jack, with its ordinary long working springs connected to theservice instrument. It will be seen that the indicator coil is disconnected untila plug is inserted in the service-jack, the service instrumentbeing at the same time disconnected from the exchange line.A 2-way cord with plug at each end is used for connecting.The other lines, called extension lines, are joined up as shownon the right of the figure, each with a tubular drop per-manently connected across

the practical telephone handbook and guide to the telephonic exchange 1906 book illustrations telephone images from internet archive

1906

Northeastern University, Snell Library

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public domain