The Encyclopedia Americana Volume 26; A Library of Universal Knowledge

Group, Books

ISBN 10: 1236373758 / ISBN 13: 9781236373755

Published by Lightning Source UK Ltd, 2012

About this Item

Zustand: Sehr gut | Sprache: Englisch | Produktart: Bücher.

Seller Inventory # 38705169/202

Bibliographic Details

• Title: The Encyclopedia Americana Volume 26; A Library of Universal Knowledge
• Publisher: Lightning Source UK Ltd
• Publication Date: 2012
• Language: English
• ISBN 10: 1236373758
• ISBN 13: 9781236373755
• Binding: Soft cover
• Condition: Sehr gut
• Seller catalogs:
  • Bücher

About this title

Synopsis

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...of special design were found to be necessary if successful results were to be obtained. In this service, besides difficulties due to packing, precautions had to be taken to annul engine, propeller and other external noises. To this end the diaphragm of one type of transmitter is so constructed as not to respond readily to air vibrations below 200 or above 2,000 per second. In another type a perforated plate is interposed between the speaker's mouth and the diaphragm of the transmitter, which device baffles the movement of extraneous sound waves toward the diaphragm while the voice waves spoken directly into the mouthpiece are not impeded. Still another device employed in this service consists in leaving the back of the transmitter open in such a way that exterior noises impinge on the back and front of the diaphragm of the transmitter with equal strength, effecting no result, whereas the voice waves hit the diaphragm in one direction only and thus set up the required variations in the transmitter circuit, even although at such times the pilot or observer cannot hear his own voice. Three Electrode Vacuum Tube Oscillator.--As previously intimated the De Forest three electrode vacuum tube is now used as a source of high frequency sustained oscillations, and many different arrangements of circuits have been designed to utilize this remarkable feature of these tubes, now in practice frequently designated vacuum tubes or VT's. One such arrangement of circuits to obtain sustained oscillations is shown in simple form in Fig. 4, termed a vacuum tube oscillator. It illustrates the "feed back" or "regenerative" coupling of circuits, perhaps first devised by Armstrong. F is the usual filament, G is the grid, P is the plate of the tube proper. HB is ...