The practical telephone handbook and guide to the telephonic exchange (1906) (14753067051)

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:

y.—A very good form of dischargekey is shown in Fig. 435. Two brass levers with longinsulating handles are pivoted to move horizontally on the ELECTRICAL MEASUREMENTS 459 top of ebonite pillars. The end of each of the levers can makecontact with a centre brass piece or with one side of a doublecontact plate. The centre contact is not generally used, andcan be moved out of position. The long-handle lever isgenerally connected to galvo, through short-circuit key andshunt-box, the short handle to battery and the double contactplate to a plug switch for connection to cable, standard con-denser, or standard resistance. The handles are moved to theleft to charge, and to the right to discharge; and a small rod ofebonite fitted in one of the handles enables both to be movedtogether, and keeps the end of the levers from contact. Plansof two of these instruments are shown in Fig. 438. The Capacity Constant is obtained as shown in Fig.436, using another form of discharge key known as ^T^ CQN-r

Text Appearing After Image:

Fig. 436.—Connections for Capacity Constant the Kempe. The battery is connected to the bottom contact of the discharge key through the battery reverser. The lever of the discharge key connected to one terminal of the condenser is pressed down, and the condenser thereby charged. After about 15 seconds the discharge trigger is depressed, the lever springs up against the top contact, and the condenser discharges itself through the galvanometer, shunted, if necessary, to give a convenient deflection, which latter is only a momentary one. The short-circuit key must be kept open. Suppose the illuminated spot is thrown 720° by the discharge, this, divided by the capacity of the condenser, 720say 0*5, gives —-=1440°, which would be the deflection given O by 1 microfarad capacity. The deflections produced by other2g 460 PRACTICAL TELEPHONE HANDBOOK capacities, divided by this number, will give the measure ofthose capacities. Thus, suppose a cable wire (with farther endinsulated) joined u

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1906

Northeastern University, Snell Library

http://commons.wikimedia.org/

public domain