The practical telephone handbook and guide to the telephonic exchange (1906) (14569780937)

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:

the most practical. Heavisides leakance distortionless circuit is theoretically the moreperfect of the two as regards distortion only, but unfortunatelyit entails a larger attenuation in general and in the case of thesmall conductors used in telephone cables a much larger attenua-tion than in the normal circuit. On the other hand the in- LONG-DISTANCE LINES— PUPIN SYSTEM 407 ductance line has a smaller attenuation besides approximatingto the distortionless conditions. As a good volume is asessential as clearness it is clear that the inductance loadingis the better solution of the problem. Sine Wave.—In order to understand Pupins theory it isnecessary to understand what is meant by a sine wave.In Fig. 402 the wave form a a a represents such a sine wave,such as may be generated by the steady revolution of thearmature of a magneto-generator such as shown at Fig. 402.The circles on the left represent the angular motion of thearmature to produce the wave, and the dotted lines show how

Text Appearing After Image:

Fig. 402.—Sine Wave Diagram the wave curve is plotted from the angles. Distances measuredto the right represent the time taken in making the revolution.Although telephonic speaking waves are of a very compli-cated nature, it has been found that they are all compoundedof a number of such simple sine waves of various frequencies. The smaller waves ceo and d d d show the nature ofadditional waves which are added, and modify the shapeof the original wave when capacity and inductance are presentin a circuit. It will be noticed that the capacity wave c c c is at itsgreatest positive value at the same time that the inductancewave is at its greatest negative value, and it is easy to see thatif both effects acted equally in the same circuit the two would 4o8 PRACTICAL TELEPHONE HANDBOOK neutralise each other, and the original wave would travel onunaffected. It will also be seen that any point of the capacity-wave c c c is 90° earlier, and any point of the inductancewave d d d is 90° later,

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

1906

Northeastern University, Snell Library

http://commons.wikimedia.org/

public domain