The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 467
rap, and outer leather case for protection.The connections are as shown in Fig. 414. Inspections of Instruments.—In order to ensure that theinstruments are kept up to a proper state of efficiency, it isnecessary that there shall be regular systematic examinationsof all sub-station instruments,… … ^ Fig. 414.—Connections of Portable Test Set made of the date of inspection and the condition, for whichpurpose special cards are provided for each instrument, onesuch being kept at the instrument and another at the exchange,where they are kept in numerical order in a proper card-index file, so…
Telephone
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