History and Function of Telegraph, Cellular Telephone, and Computer
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TEXTO 1 • TELEGRAPH
Telegraph, an electrically operated device or system for distant communication (the first ever invented) by means of visible or audible signals. The method used throughout most of the world, based in large part on the mid-19th-century work of Samuel F.B. Morse, utilizes an electric circuit set up customarily by using a single overhead wire and employing the earth as the other conductor to complete the circuit. In the telegraph's simplest form, an electromagnet in the receiver is activated by alternately making and breaking the circuit. Reception by sound, with the Morse code signals received as audible clicks, is the basis for a low-cost, reliable method of signaling. In addition to wires and cables, telegraph messages... Continue reading "History and Function of Telegraph, Cellular Telephone, and Computer" »