File:Electrical instruments and telephones of the U.S. Signal corps (1911) (14569857439).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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ust be observedin the operation and maintenance of the Duro storage battery: 1. Always carry in a vertical position. 2. Battery should have a thorough discharge every six Aveeks. 3. Vents should always be kept tight when in use. 4. When charging, open vents, add enough pure water to bringlevel halfway up to hole. Leave out corks while charging and replacewhen charge is completed. Chapter III. THE MORSE TELEGRAPH. The two methods of arranging the ordinary Morse circuits arecalled the open and closed circuit systems. The latter is frequently called the American s^^stem, the diagram ofwhich is given in figure 21. In this only one line battery is necessary,although in practice it is found better to divide the battery betweenthe terminal stations as shown, care being taken not to connect thebatteries in opposition. Each key is furnished with a circuit-closerlever, and when the line is quiet the current is constantly nuining.keeping the relays and sounders closed. When any station opens his
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1 Fin. 21. circuit by means of the lever, he controls it entirely with the key.This system is in universal use in the United States and Canada. The diagram of the open-circuit system is given in figure 22. Inthis system each station maist have sufficient main-line battery to workthe line. The keys have a front and a back contact. (See fig. 25.)When the line is quiet, there is no current running, and when any sta-tion depresses his key he breaks the back contact and introduces hismain-line battery through the front contact, operating the relayson the line. The relay is frequently put in the back-contact circuit,in which case the operator does not work his own relay, thus cutting60 ELECTRICAL INSTRUMENTS U. S. SIGNAL CORPS, 61 its resistance out of the circuit, but the American operator prefersto hear his own instrument work. This system has been used exclusively on the short signal-corpssubmarine cables. It obviates the constant application of battery tothe cable, as would result from

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