Page:The New International Encyclopædia 1st ed. v. 18.djvu/194

SIGNALING AND TELEGRAPHING. 156 SIGNALING AND TELEGRAPHING. or double) made of white canvas stretched on rings or hoops of wire and attached to a light stati', and semaphores consisting of a post with 4 A B SEMAPHOREa. a, for day ; b, for night. arms movable by ropes, each position represent- ing a letter or number. These may be used at night by attaching lanterns to the arms. Signal flags on halliards, stationary or by motions, are also frequently used, as is discussed under Signals, Marine. At night signals may be made by candle ioinbs, which are pasteboard shells charged with bril- liant stars, fired from bomb guns or mortars or signal rocl;ets, which under favorable circum- stances can be used up to ranges of about eight miles. Kockets are most efficiently employed as chronosemic or time interval signals. Signal composition fires are pyrotechnic compositions which burn with great intensitj' of light and color, generally red, white, and green. To observe all these visual signals it is necessary to employ powerful and portable telescopes. The sig- nal telescopes for use at long ranges magnify about 30 times and have a focal length of 2G inches. The glass is strong. Binocular glasses are also useful, as they combine a low magnifying power with a large field. The new 'porro prism' glasses are now issued to the United States Signal Corps. Ciphers. A signal cipher is a method of or key to secret signaling understood only by those concerned. In the presence of the enemy the necessity for its use is apparent, and in order to secure secrecy it must frequently be changed. PIGNAL DISK. Naturally there are countless forms and systems of ciphers. Among these is the signal disk, which is a device for readily enciphering and decipher- ing a message. It consists of a small disk of cardboard or other material, on which are writ- ten or printed the letters of the alphabet in irregular sequence and arranged around the cir- cumference of the disk. These letters are so placed that when the disk is properly held all the letters are upright. On this small di.sk are also printed those combinations of letters which frequently occur in words, as "tion,' 'ing,' 'ous,' etc., and a sign to mark 'the end of the word.' On a larger disk are written or printed, arranged around its circumference in the same manner, either the letters of the alphabet or the symbolic numbers of signals which are to be used. The disks are fastened concentrically together in such manner that one may revolve upon the otlier and that they may be clamped in any position. They are of such size that when so fastened the letters, etc., upon the inner disk will each appear close to and directl.y opposite one of the signal combinations upon the outer disk. The figures '1' and '8' are sometimes used in- stead of the figures '1' and '2' to symbolize the elements 'one' and 'two.' because the figure '8' is upright in most positions of the disk. Having a disk so arranged and clamped, it will be clearly understood by any signalist that, so provided, he has before him an alphabetic code with every letter opposite its signal symbols. And he will comprehend that, by referring to the disk, he can transmit a message without the study of any par- ticular code and can transmit it in secret signals or cipher by moving the disks upon each other. Military Telegraph. The electric telegraph for the transmission of signals came into prac- tical use about 1S3.5. Its history and develop- ment will be found discussed in the article Iele- GRAPH. Beyond saj'ing that the Morse system makes use of a code of three elements, dot, dash, and space, as shown above, it is necessary here to concern ourselves merely with strictly mili- tary lines. With the invention and general use of the telephone came its application to warfare, and this instrument, too, has been specially adapted for this purpose. Military lines for telegraph or telephone field service are generally called 'flying lines.' They are strung on light poles called 'lances,' "2 1/4 inches in diameter and 17 feet long, placed 2 feet in the ground, and about 40 per mile are necessary. Instruments and material are transported by wagons designed for the purpose to accompany the army in the field. These constitute the field telegraph train. For quick work at the front the wire is on reels, carried either on a man's back or on a light cart. The wire is light, strong, and pliable, generally a steel core with copper sheathing, and for the lighter lines is not even insulated. By the use of high frequency currents this bare wire, rapidly reeled off on the ground, constitutes the conductoi' for the special 'vibrator' forms of telegraph and telephone instruments now used by the United States Signal Corps. The speci.al apparatus used by the Signal Corps exhibits many modifications from the accepted commercial practice. One of the most important of the instruments used is the 'buzzer.' which is constructed in forms suitable for regular service or for the field. It consists of a telephone re- ceiver and transmitter, a vibrator and induction coil, condenser, telegraph key and switches, and four cells of dry battery. This instrument is used for connecting with rapidly constructed field