The practical telephone handbook and guide to the telephonic exchange (1906) (14753891564)

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:

48a shows the con-nections of the instrument,which comprises two bar-retters b and b,, a 2-mf. condenser O, two inductances i, a long range potential divider d and avery sensitive moving coil galvanometer with shunt. B is the work-ing barretter and b1 the balancing one. The alternating speakingcurrent is connected to the bridge through a condenser, and the in-ductances prevent its passage through the galvanometer, etc. Analternating current of 15 micro-amperes will deflect the galvano-meter 5 divisions, and the same strength in direct current will give adeflection of 150 divisions. For measuring alternating current theinstrument is set up as shown, the potential divider is then rotateduntil the galvanometer is at zero, and then the alternating currentsconnected to the line terminals produce deflections which are pro-portional to the square of their strengths. Cohens Barretter Set.—Two somewhat similar instruments asabove, connected to the same galvanometer,as shown in Fig. 4486, to-

Text Appearing After Image:

A5m.t I 32± Fig. 4486.—Connections of Cohens Barretter Set gether form a bridge instrument which when operated by an alternat-ing current enables the impedance of instruments, lines, etc., con-nected at a to be balanced by resistances connected to b,, or viceversa. Both these instruments are made by R. W. Paul, of New South-gate, N. CHAPTER XXX THE BRITISH INSULATED CO.S TELEPHONE SYSTEM AND LATERPOST OFFICE EXCHANGE PRACTICE The British Insulated & Helsby Cable Co. has worked outa very complete central energy system, and has equipped anumber of exchanges in this country, the chief ones beingtrunk exchanges for the British Post Office at London, Liverpool,Manchester, Birmingham, Newcastle, Glasgow and Bradford.It has also fitted up a large ordinary C.B. exchange for theB.P.O. at Cardiff and smaller ones at several other centres. The system of working is based on the Stone C.B. systemand whilst the arrangements of the ordinary exchanges followthe same general lines as those of t

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1906

Northeastern University, Snell Library

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public domain