The practical telephone handbook and guide to the telephonic exchange (1906) (14569495118)

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:

tem, but in a differentmanner. Fig. 131 shows the simplest form of the speakingcircuit without the switch-hook and bell. The loop has twobranches, in one of which is the receiver r, the secondary of aninduction coil s, and the condenser c, and in the other branchis a retardation coil, t, the microphone m and primary coil pbeing arranged as shunts to each other. The retardation coil Tprevents the undulations passing direct to line, and confinesthem to the local primary coil circuit. In a later form ofthis system the ringer coils are used in place of the specialretardation coil, and a condenser is included in the primarylocal circuit, as shown in Fig. 132. Electrolytic Cell.—In place of the condensers shown in Fig. Fig. 130 122 PRACTICAL TELEPHONE HANDBOOK 131, Messrs Siemen sometimes make use of what are calledelectrolytic or polarisation cells. These are merely small,sealed glass bulbs nearly filled with a solution of an electro-lyte such as ammonium phosphate, and having connecting

Text Appearing After Image:

Fig. 131 Fig. 132 wires of platinum cemented through the glass, and solderedto two small aluminium electrodes, as shown in Fig. 133.Like condensers, these cells have the property of allowingthe apparently free passage of rapidly alternating currentsbut of completely stopping any direct current. An aluminiumplate in certain solutions has the peculiar property of allow-

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1906

Northeastern University, Snell Library

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public domain