e signals by which information of anykind may be given or received. The sending operatorcontrols the current by the key. This consists of a plati-num contact point so mounted on a lever that it will closethe circuit when the knob is pushed down. By pushingthe key down, the sending operator causes… … Fig. 117. key, the armature of the sounder is pulled down with aclick; and when the key is raised, the current is stoppedand the armature springs up, causing a different click. When the line is very long or a great many instru-ments are to be operated at once, the current may not bestrong enough to…
Physics
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![An illustration from [Electric engineering.] (1902)](https://img.insideoutlibrary.com/img/200/ia-electricengineer01inte-490-194.webp)
