File:Electrical instruments and telephones of the U.S. Signal corps (1911) (14756596875).jpg

Identifier: electricalinstru00unitrich (find matches)
Title: Electrical instruments and telephones of the U.S. Signal corps
Year: 1911 (1910s)
Authors: United States. Army. Signal Corps
Subjects: Military telegraph -- United States Military telephone -- United States
Publisher: Washington, Govt. print. off.
Contributing Library: University of California Libraries
Digitizing Sponsor: MSN

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n with a card of instructions and the wiring dia-gram on its inner surface. The front side of the box is hinged at thebottom and opens out and acts as an operating shelf on which thesending key is mounted. The circuits of the set are shown in figure205. Bv reference to this fiirure it will be seen that there are three ELECTRICAL INSTRUMENTS U. S. SIGNAL CORPS. 297 principal circuits: First, the primary circuit, couiprisin<i; sending key,three cells of battery, and coarse wire winding of the induction coilin series; second, the secondary circuit, comprising the two Avindingsof the polarized relay in series, the fine wire winding of the inductioncoil, line and ground connections: third, the local sounder circuit,comprising one cell of local battery, battery switch, sounder and relaycontacts in series. The operation of the set is as follows: When thesending key is closed, battery flows through the coarse wire windingof the induction coil, inducing a momentary current in tlio fine wire
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Fir,. 204.—Field iiuliictiou set. winding which passes through the rela) windings and a similar cir-cuit at the distant station. The relay contacts are closed during thetime this current flows and remain closed until the key is opened,when the discharge of the induction coil being in the opposite direc-tion- from the original current o)iens the relay contacts and releasesthe sounder. The advantages of the field induction telegraph set arethe ease of continuous sending with the standard telegraph key, theaudible signals j^roduced by the local sounder circuit, and the sensi-tiveness of the polai-ized relay to a small current. The speed in send- 298 ELECTRICAL TNSTKUMENTS U. S. SIGNAL CORPS. in« is also ffronter than is possible with the various types of buzzers.On the othei hand, the instiuinent ivc^uires more careful adjustmentfor satisfactory service and is moi-e difficult to maintain in perfectoperatinc: condition. ^AA/WVW\P

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