simpler transmitter and receiver of the earlier experiments. Many patents on this line have been taken out, but no public commercial test of a syntonic system has been satisfactory.
Another defect has been the slowness, largely owing to the necessity of tapping the coherer each time. A number of new wave-detectors have been recently brought into use. Marconi has invented a magnetic receiver, a figure of which is shown (Fig. IV). A steel ribbon is carried over wheels through a coil which is in the circuit AE of the receiver. The magnetic effect of the wave on the steel ribbon is read by sounds in the telephone. The Italian naval apparatus uses a form of mercury coherer; Fessenden uses a thermal receiver; while an electrolytic receiver is used by another inventor. Speeds of from 30 to 40 words per minute are claimed, but good authorities put ordinary speed now attainable as 10 to 12 words per minute. From a commercial standpoint wireless telegraphy is possible but not yet fully developed. For moderate distances it already is fairly reliable. In communicating with and between ships at sea it has proved invaluable. Many of the large Atlantic steamships are equipped with wireless outfits, and often receive messages during a large part of their trip. The Japanese-Russian war showed the advantage and the necessity of wireless telegraphy in naval operations. All United States warships are now equipped with wireless outfits, and the navy department maintains a series of wireless stations at strategic points along the coast. The German military authorities have used it in army maneuvers.
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| MAGNETIC WAVE-DETECTOR |
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Fig. IV. (R) steel ribbon carried over wheels (WW) through coil (p) in receiving circuit (AE); (T) telephone to detect magnetic effects made by wave. |
After Marconi the principal inventors in wireless telegraphy are Slaby, Arco and Braun in Germany; Fessenden and De Forest in the United States; and Lodge and Muirhead in England. For the details of these systems the patent specifications must be consulted.
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WIRELESS TELEGRAPH STATION SHOWING VERTICAL WIRES |
The leading reference-books are Fahie's History of Wireless Telegraphy; Lodge's Signaling through Space without Wires; and Turpain's Ondes Electriques. But more important are the articles in the electrical journals and the patent-office reports.
Telemachus (tĕ-lĕm′a-kŭs), in Greek mythology, the son, by Penelope, of Odysseus or Ulysses, king of Ithaca and hero in the Trojan War, who was noted for his exploits and wanderings. Telemachus, in search of his father, attended by Athené in the guise of Mentor, goes to Pylos and elsewhere, endeavoring to find him. He at last discovers him in the guise of a beggar, when Telemachus was lodging in the house of a shepherd. The king is told how his faithful wife is annoyed by innumerable suitors. Returning to Ithaca both father and son, aided by Athené succeed in slaying these suitors, after which the touching meeting takes place between Odysseus and Penelope. See Ulysses.
Telem′eter, an instrument for finding the distance of an inaccessible object. In military circles this instrument is generally called a range-finder. Nearly all telemeters are based upon one of two general principles: (1) The image of a distant object, produced by a lens, is geometrically similar to the object itself and depends for its size upon the distance of the object; (2) having chosen a convenient base-line of known length, it is possible by measuring the angle between this base and the direction of the distant object (first at one end of the baseline and then at the other) to compute the distance of the object. A great variety of these instruments have been invented, some adapted to infantry in the field and therefore compact and less accurate, others
