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Chapter 14

SIGNAL COMMUNICATIONS

No military activity can be carried on successfully unless commanders, at every level, can promptly convey their orders to their subordinates and receive information from them. In the prescientific era this was accomplished by messengers, simple visual signals, and sound signals, (bugles, trumpets, horns, whistles, etc.). The development of electrical science and electronics has multi

plied the possibilities of signal communications. Concurrently, however, the evolution of the military art, notably in the fields of wide dispersion and fast movement, has taxed those possibilities to the utmost. Atomic warfare, with its increased emphasis on mobility and dispersion, is further underscoring the need for signal communications which are reliable, secure, and adequate.

DEFINITIONS AND TYPES

Signal communications are defined as "the means of conveying information of any kind from one person to another, except by direct unassisted conversation or correspondence." The following means are used in the Army

LINE/WIRE COMMUNICATION. It utilizes a physical path between sender and receiver, such as wire or a wave guide.

RADIO COMMUNICATION. It utilizes radio waves not guided between sender and receiver by any such physical path.

VISUAL COMMUNICATION. It utilizes optical signals, such as arm or flag movements, panels, lights, pyrotechnics, smoke signals, etc.

SOUND SIGNALING. It utilizes various devices to transmit sound messages consisting of prearranged signals. (In an emergency the international Morse code may be thus used.)

MESSENGERS. These are also a means of communication. They are in general human beings, traveling on foot, on horseback, or by sea, air, or land vehicle. (Pigeons and animals have also been used to carry messages.) Messengers are trained and used by military commanders at all levels as part of the unit's routine training and operations. The same is true of certain types of visual and sound signaling. As regards the more complex techniques, including line/wire and radio communications and allied applications of electronics, the equipment is provided by the U.S. Army Signal Corps, and the operating and maintenance personnel belong to, or are trained by, that Corps. It is with this field of signal communications that the present chapter is mostly concerned. (For further information on the Signal Corps see also chapter 2.)

EVOLUTION OF SIGNAL COMMUNICATIONS

Systematic progress in signal communication in our Army dates from the Civil War.

CIVIL WAR. In that war, signaling by wigwag flags and torches was extensively used. Major A. J. Myer introduced insulated field wire and a portable electric set (the Beardslee magnetoelectric machine), perhaps the first such portable unit ever designed for military purposes. Its use in the war, however, was far overshadowed by another wire-telegraph organization, the U.S. Military Telegraph. This was a civilian organization, but it was controlled by the Secretary of War and officered by a few former telegraph company men commissioned in the Quartermaster Corps. Using commercial telegraph equipment (while adopting some of the field telegraph techniques which Maj. Myer had developed), it constructed, up to June 1866, a total of 15,389 miles of wire line for the Army, of which 1,000 miles were temporary field lines and 178 were submarine-cable lines.

POST-CIVIL WAR PERIOD. The Signal Corps obtained control of Army telegraph lines soon after the war, and extended them to Army camps and posts throughout the western territories (later, from 1900 on, to the Alaska frontiers also). Possession of these lines by the Corps led Congress, in 1870, to assign to it the responsibility for national meteorological duties and daily weather reporting. While its telegraphers at Army posts throughout the country doubled as weather observers, the Corps, under the leadership of such pioneer meteorologists as Cleveland Abbe, created the first truly national weather service (transferred to the Department of Agriculture, as the Weather Bureau, in 1891). During the period of its weather service it contributed notably to the First Polar Year, 1882-3 (actually the first "international geophysical year"), sending scientific observers to Point Barrow, Alaska, under Lt. P. H. Ray (1881-3), and to Ellesmere Island, northern Canada, under Lt. A. W. Greely (1881-4).

In the late 1870's the Corps used heliograph signaling. Following Bell's invention it adopted the telephone. Balloons

for observation and signaling became a Corps responsibility about 1890. In the Spanish-American War the Corps used both telephone and telegraph. That war took it to Cuba, Puerto Rico, and the Philippines, where its men installed and operated land lines and submarine cable.

WORLD WAR I. In that war the Signal Corps greatly expanded its services to the Army, providing telephone, telegraph, radio, and pigeon communications. It also set up photographic and meteorological services, and took its first steps in enemy intercept and direction finding (then called goniometry). Besides laying many thousands of miles of field wire (Signal Corps outpost companies installed and operated the equipment up to the front lines), the Corps literally crisscrossed all France with fixed installations, building 1,724 miles of permanent pole line. By November 1918 it was operating 273 telephone exchanges (which grew to 328 by February 1919) and 144 telegraph offices. From the latter part of 1917 to 1 January 1919, the system handled a total of 7,601,500 telegrams, 870,000 long-distance telephone calls, and 25,184,500 local calls.

DEVELOPMENT OF RADIO AND RADAR. The first experimental radio transmission by the Corps over appreciable distances began in 1899. At its laboratories at Ft. Monmouth, N. J. and at Dayton, Ohio, the Corps during the 1930's developed Army radar types and made a beginning with aircraft radio and navigational equipment and with FM vehicular (tank) radios of the SCR-500 and -600 types. All these developments greatly expanded after Pearl Harbor.

THE ARMY'S RADIO NETWORK. The development of the worldwide radio network which the Army uses today began with the War Department Radio Net, which the Signal Corps set up in 1921. It handled 3,800,000 words in that first year, and 26,500,000 by 1933. The net expanded enormously in the 1940's, when its title was changed to Army Command and Administrative Network (ACAN). In 1941, ACAN included Seattle (serving the Alaska Communications System) and oversea Army

stations at San Juan, Puerto Rico, in Panama, and at Honolulu and Manila, and was handling half a million words a day. By 1945 the ACAN stations encompassed the world, and had a capacity of up to 100,000,000 words a day.

During and after World War II, military wire and radio communications were integrated. Carrier systems multiplied the capacity of wire and radio circuits. In the course of World War II the Signal Corps made increasing use of radio teletype and radio relay; the latter, rather than wire, proved at times

to be the mainstay of Army communications. (This was increasingly true, a few years later, in Korea.)

SUPPLY IN WORLD WAR II. In the six calendar years 1940-45 inclusive the Signal Corps procured for the Army some seventeen billion dollars' worth of equipment and supplies. The following summary table shows the total numbers of various major categories of equipment procured in that period (except that, for a few items, data are incomplete, or exclude part of the sixyear period, etc.).

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Although the basic duty of the Signal Corps is to provide military communications, it has traditionally taken on many additional allied technical duties for the Army. One example is military photography. The Army's pictorial records of all conflicts since the Spanish-American War have been made by Signal Corps photographers. The Signal Corps Pictorial Center, in its studios at Astoria, Long Island, N. Y., produced 2,650 motion pictures and 1,458 film strips for training purposes between 9 March 1942 and 31 July 1945. These were distributed by the Army Pictorial Service, and were a vital aid in the training of troops. The Pictorial Service also handled photomail and V-Mail letters,

photographing about a billion and a quarter of the latter between June 1942 and August 1945.

Military aviation in the United States had its genesis in the Aeronautical Section of the Signal Corps which was established on 1 August 1907. It remained under Corps control until May 1918, when the Army established a separate Air Corps. The first flight of an airplane (piloted by O. Wright) on a military installation occurred on 3 September 1908, at Ft. Myer, Va. Following its crash on 17 September, fatally injuring Lt. T. E. Selfridge, on duty with the Signal Corps for aviation service (the first man ever killed in heavier-thanair powered flight), the Wrights pre

sented in July 1909 a second military plane, which filled their contract with the Signal Corps.

Recently the Corps has acquired Army television responsibility. The allied techniques of photography, television, radar, infrared, and other devices have combined to produce the

Army's Combat Surveillance program, a new Signal Corps responsibility. In 1952 the Corps opened Fort Huachuca, Arizona, as the Army Electronic Proving Ground, where new methods and equipment embracing a wide span of communications-electronic activity are being tested.

INSTALLATION AND HANDLING OF MILITARY COMMUNICATIONS

MESSAGE CENTERS. The communications system serving any Army headquarters has its focus in the message center. A message center has the following functions

1. Handling all messages to or from the headquarters, except those transmitted direct by the originator or handled by military or civil post; and keeping records thereon.

2. Selecting the means of transmitting messages, checking on their flow, and reporting to the originator any undue delay in transmission.

3. Coordinating the means of communication and checking on their effectiveness.

4. Observing security regulations.

5. Keeping up-to-date information on where unit command posts are located and how to reach them.

6. Keeping the official time of headquarters.

RADIO NETS. Military radio sets are operated in "nets." Sets which can work together because of similar frequency settings, similar type of signal (“CW", "MCW" or "voice"), and similar type of modulation (FM or AM) are said to be capable of netting with each other. A net is formed when two or more stations operate on the same frequency and can intercommunicate. Each station has a call sign, which is periodically changed. In forming a net, definite procedures are required to adjust its equipment, control transmission, and clear the messages. There is a net control station (NCS), the duties of which are to open and close the net and maintain discipline within it. Sometimes an alternate control station (NCS 2) is desigated. Army units (for example, infantry, armored, and airborne divisions,

and many other larger and smaller commands) each have their characteristic nets or groups of nets, determined by the need which the elements composing the unit have to communicate with each other. These nets are of various types. Command nets connect the unit commander with his subordinate commanders. Reconnaissance and Surveillance nets are intended to give staff officers the information on which combat intelligence is based. A number of different support nets are needed: for example, to furnish firing data to gun batteries, to provide unit headquarters with channels for administrative communications, and so on.

COMMUNICATIONS

DISCIPLINE.

Since radio communications can be intercepted by the enemy, communications discipline and crytographic security are vital to prevent him from acquiring useful information by listening to radio traffic. Communications discipline involves the proper use of radio equipment, good net control, and the meticulous training of radio operators. It requires that operators use only the radio frequencies which have been allotted to them, and that they follow explicitly the details of the operating procedures which have been laid down for them. It involves careful monitoring of their radio transmissions. An important aspect of communications security is cryptosecurity, involving, for example. the proper use of codes and ciphers to deny the enemy any knowledge of the content of radio communications. Good cryptosecurity depends upon the use of approved cryptosystems, strict adherence to crypto operating instructions and procedures, the assignment of qualified and trained personnel to crypto duties, the

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