The Project Gutenberg eBook ofVisual SignalingThis ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: Visual SignalingAuthor: United States. Army. Signal CorpsRelease date: August 20, 2013 [eBook #43515]Most recently updated: October 23, 2024Language: EnglishCredits: Produced by Chris Curnow, Emmy and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)*** START OF THE PROJECT GUTENBERG EBOOK VISUAL SIGNALING ***
This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.
Title: Visual SignalingAuthor: United States. Army. Signal CorpsRelease date: August 20, 2013 [eBook #43515]Most recently updated: October 23, 2024Language: EnglishCredits: Produced by Chris Curnow, Emmy and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
Title: Visual Signaling
Author: United States. Army. Signal Corps
Author: United States. Army. Signal Corps
Release date: August 20, 2013 [eBook #43515]Most recently updated: October 23, 2024
Language: English
Credits: Produced by Chris Curnow, Emmy and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK VISUAL SIGNALING ***
WAR DEPARTMENTOFFICE OF THE CHIEF SIGNAL OFFICER——————MANUAL No. 6
WAR DEPARTMENTOFFICE OF THE CHIEF SIGNAL OFFICER——————MANUAL No. 6
VISUAL SIGNALINGSIGNAL CORPSUNITED STATES ARMY1910United States of America War Office Emblem
SIGNAL CORPSUNITED STATES ARMY1910
United States of America War Office Emblem
WASHINGTONGOVERNMENT PRINTING OFFICE1910
WASHINGTONGOVERNMENT PRINTING OFFICE1910
WAR DEPARTMENT,Document No. 366.Office of the Chief Signal Officer.
War Department,Office of the Chief of Staff,Washington, April 20, 1910.
The following Manual of Visual Signaling, prepared in the Office of the Chief Signal Officer, is approved and herewith published for the information and guidance of the Regular Army and the Organized Militia of the United States, and supersedes all other pamphlets or similar instructions heretofore issued upon the subject. Officers and men of the Signal Corps will thoroughly familiarize themselves with the instructions and suggestions contained herein.
By order of the Secretary of War.
Tasker H. Bliss,Brig. General, General Staff,Acting Chief of Staff.
Page.Chapter I.—Introduction9Chapter II.—Visual signaling equipment.The wand11The flag kit:The 2-foot flag kit12The 4-foot flag kit12Care of flag material13Powers and limitations of flag signaling13The heliograph:Historical14Description14Assembling17Adjustment20Operation21Care of apparatus22Powers and limitations of the heliograph22The signal lantern:Acetylene23Calcium carbide23Method of gas generation24Description25Operation and care30Powers and limitations of the signal lantern35Rockets and shells:Description35Operation38Employment40The semaphore: Description40The searchlight: Methods of employment41The Coston signals41Very's night signals42The Ardois system of signaling42Sound signals44Improvised signal methods44Chapter III.—Alphabets or systems of signals.Signal alphabets:American Morse45Continental Morse45Army and navy45Abbreviations46Code calls47Execution of signal alphabets47The army and navy alphabet47The Morse alphabets49International code of signals:Description51Two-arm semaphore51The Ardois system52Coston signals54Very's night signals54Rocket signaling55Two-arm semaphore alphabet, U. S. Navy57Summary of signals, army and navy alphabet60Chapter IV.—The field message.Definition64The blank form64Writing the message66Instructions to operators:Use of message blank66Duties of sending operators66Order of transmission66Duties of receiving operators67Communications confidential67Checking the message67Chapter V.—The signal station.Location of stations:General considerations68Backgrounds70Azimuth of stations71Altitude71Determination of background color72Choice of apparatus73Miscellaneous considerations73Intervisibility table74Finding a station75Operation of stations:Personnel76Calls and personal signals78Opening communication79Commencing the message80Sending and receiving80Breaking80Discontinuance of transmission81Acknowledgment of receipt81Station records81Formation of signals82Repeating the message83Signal practice83Chapter VI.—Codes and ciphers.Codes in use84Employment of codes84Cipher code85The War Department Code86Cipher code in field work87Field ciphers:Description and use87Forms of field cipher88Inversions88Concealment of terminations88Cipher apparatus: The cipher disk89The mathematical cipher93The route cipher94Cipher detection: Employment of cipher disk96Chapter VII.—Field glasses and telescopes.Reflection98Refraction98Lenses98Focus99Optical center99Image99Conjugate foci99Law of foci100Formation of image101Spherical aberration102Chromatic aberration102Telescopes104Galilean field glasses and telescopes106Porro prism field glasses and telescopes106Field glasses108Properties of telescopes and field glasses109Power109Light111Field114Definition115Field glasses and telescopes issued by the Signal Corps119Type A121Type B124Type C125Type D125Field-glass specifications126
INTRODUCTION.
While, in consequence of the development of electrical invention and improvement, visual signaling will be less frequently resorted to in future than heretofore in the service of field lines of information, it should be appreciated that the necessity for an adequate supply of apparatus of this kind, and the need for skilled manipulators to operate it, has in no wise diminished. The great celerity with which electric signals can be exchanged and their usual entire independence of local conditions has placed systems of this class foremost among the signaling methods of the world. There is scarcely any commercial industry whose successful existence does not vitally depend upon some one, perhaps several systems of signaling, and improvements of old and inventions of new signal devices are continually necessary to meet the requisite needs demanded by the progress of art and science. Railways are probably the greatest of all commercial users of signals. With them the great mass of intelligence is transmitted by the electric telegraph and telephone, but the flag, the semaphore, the signal light, and many other contrivances furnish indispensable visual adjuncts. Visual signaling is and always will be a most valuable means of transmitting informationin peace and war, and it is not to be imagined that it will ever be supplanted in its particular function by the introduction of other methods. Occasions will frequently occur in the field when no other means will be practicable, and then, if not before, will the value of the system be fully emphasized.
Strictly speaking, a visual signal is any visible sign by which intelligence is communicated, but in a military sense the term visual signaling has a broader meaning and includes other methods of transmitting information than those which appeal to the sense of sight.
In most systems of signals suitable for military use, each signal is composed of one or more separate units, known as elements. Having prescribed a certain number of elements, the various signals are formed by having these elements appear singly or together in different arrangements or combinations. The continental system is one of two elements, namely the dot and the dash, while the Morse system employs three elements, the dot, the dash, and the space. Having agreed upon a certain number of combinations of elements, a system of signals is formed by giving a meaning to each combination. These meanings usually include the letters of the alphabet and numerals, combinations of which being used to formulate necessary information. Combinations of elements of any system can also, however, be used to indicate any desired meaning.
With reference to period of visibility, signals are of two kinds, transient and permanent. A transient signal is one which disappears as soon as completed;a permanent signal is one that remains in view for some time. Heliograph signals are transient signals, while signals made by code flags are permanent signals. Signals are divided into classes in accordance with the number of elements employed in their formation. Thus, signals using two elements are signals of the second class, signals using three elements signals of the third class, etc.
The standard apparatus used in visual signaling is fully described in a succeeding chapter. Some of the instruments employed are used wholly for day, and some wholly for night, signaling. Some devices, either with or without slight variations, are equally well adapted to day or night work. Visual signaling presents a great field for ingenious and resourceful work, and emergency will often demand the advantageous employment of other methods than those described herein.
VISUAL SIGNALING EQUIPMENT.
The wand is a stick of light wood about 18 inches long and one-half inch in diameter. It is held loosely between the thumb and forefinger and waved rapidly to the right or left to indicate the elements of the alphabet. It is used for practice purposes and the signals made by it are only intended to be read at very short distances.
Two kinds of flag kits, the 2-foot kit and the 4-foot kit, are issued by the Signal Corps.
The 2-foot kit.—This kit consists of one white and one red signal flag, two three-jointed staffs, and a suitable carrying case to contain the outfit. The white flag is made of white muslin 2 feet square, with an 8-inch turkey-red muslin center. The red flag is of similar size and material, the only difference being an alternation of colors in the body and center. The means of attachment to the staff consists of a loop at the center, and two ends of white tape at each edge, of the back of the flag body. The staff is made of hickory in three joints, each 23 inches long, and is assembled by telescoping into brass ferrules. Brass eyes are provided on the first and second joints to receive the tape ends at the edge of the flag. The carrying case, of convenient size and shape to contain the two flags and staffs complete, is made of 8-ounce standard khaki bound with leather and fitted with a shoulder strap.
The 2-foot kit is essentially a practice kit, although under favorable conditions of weather and terrain it may be used to advantage as a short distance service signaling outfit. Two of these kits are issued to each troop, battery, and company for the purpose of disseminating general instruction in military signaling throughout the army.
The 4-foot kit.—This kit is of essentially the same description as the 2-foot kit except as regards size. The flags are 3 feet 9 inches square with 12-inch centersand the staffs are considerably heavier, the joints being each 36 inches long. The 4-foot kit is the standard field flag kit and the range at which signals can be exchanged with it depends on a variety of factors, such as the condition of the weather, the location of stations, the proficiency of signalmen, etc. The speed for continuous signaling is seldom greater than five to six words per minute.
Care of flag material.—Signal flags should be examined at the close of drill or practice and repairs made to any rents or loose ties discovered. Flags, when soiled, should be thoroughly washed and dried in the sun. Signals made by clean flags are much more easily read than those made by dirty ones. Staffs should be handled with care, especially when jointing or unjointing. Care should be taken not to bruise the ends of the brass ferrules. If a ferrule becomes loose on a staff it should be tightened without delay.
Powers and limitations of flag signaling.—The advantages which may be claimed for this method of signaling are portability of apparatus, adaptability to varied weather conditions, and great rapidity of station establishment. The disadvantages are the lack of celerity of the signals, their impenetrability to dust or smoke, and the comparatively short ranges at which they can be read.
The heliograph is an instrument designed for the purpose of transmitting signals by means of the sun's rays.
Historical.—Experiments with the heliograph with a view to its adoption as a part of the visual signaling equipment of the United States Army were commenced as early as 1878. The reported successful use of the instrument by the British in India about this time led to the importation of two heliographs of the Mance pattern. A series of experiments with these machines conducted for the purpose of eliminating certain objectionable features finally resulted in the evolution of the present type of service heliograph.
The early English heliograph was not provided with a shutter, the flash being directed on the distant station by means of a movable mirror controlled by a key. The great objection to this type of instrument was the impossibility of maintaining accurate adjustment during the transmission of signals due to the fact that the manipulation of the mirror tended to throw the flash constantly out of alignment. To overcome this, the American heliograph has been provided with a screen designed to operate as a shutter and control the flash reflected from an immobile mirror.
Description.—The service heliograph equipment of the Signal Corps consists of:
A sole-leather pouch with shoulder strap containing—1 sun mirror.}Inclosed in a wooden box.1 station mirror.1 screen, 1 sighting rod, 1 screw-driver.A small pouch, sliding by 2 loops upon the strap of the larger pouch, containing 1 mirror bar.A skeleton leather case containing 2 tripods.
A sole-leather pouch with shoulder strap containing—
1 sun mirror.}Inclosed in a wooden box.1 station mirror.1 screen, 1 sighting rod, 1 screw-driver.
A small pouch, sliding by 2 loops upon the strap of the larger pouch, containing 1 mirror bar.
A skeleton leather case containing 2 tripods.
photoFig. 1.—Heliograph assembled.
Fig. 1.—Heliograph assembled.
The mirrors are each 4½-inch squares of plate glass supported by sheet brass and cardboard backings, and mounted in brass retaining frames. At the center ofeach mirror there is an unsilvered spot three thirty-seconds of an inch in diameter and holes corresponding to these spots are drilled in the backing. The sun mirror differs from the station mirror only in that ithas a paper disk pasted upon its face covering the unsilvered spot. The mirror frames are carried by brass supports provided at the bases with conical projections accurately turned to fit the sockets of the mirror bar and grooved at the ends to receive the clamping spring. Each support is fitted with a tangent screw and worm wheel attachment functioned to control the motion of the mirror frame about its horizontal axis.
drawing carrying casesFig. 2.—Mirror and mirror bar case.
Fig. 2.—Mirror and mirror bar case.
The mirror bar is a bronze casting provided at the center with a clamp threaded to fit the screw of the tripod. By releasing the clamp the bar may be moved independently of the screw and adjusted to any desired position. Conical sockets for the reception of the mirror supports are provided at the ends of the mirror bar. These sockets work freely in the bar and, being actuated by a tangent screw and worm wheel, serve to regulate the motion of the mirror frame about its vertical axis. Clamp springs, for engaging and securing the ends of the mirror frame supports, are attached at each end of the bar.
The screen is a brass frame 6½ inches square, in which six segments or leaves are mounted in such a way as to form a shutter. The leaves are designed toturn through arcs of 90° on horizontal axes, unanimity of movement being secured by connections made with a common crank bar. The crank bar is operated by a key and retractile spring which serve to reveal and cut off the flash. A set screw and check nut at the lower edge of the screen frame limits the motion of the crank bar and the opening of the leaves. A threaded base support furnishes the means of attaching the screen frame to the tripod.
The sighting rod is a brass rod 6½ inches long, carrying at the upper end a front sight and a movable disk. About the rod is fitted a movable bronze collar, coned and grooved to take the socket and clamping spring of the mirror bar. A milled edged bronze washer serves to clamp the collar to the rod at any desired point.
drawing carrying caseFig. 3.—Heliograph tripods.
Fig. 3.—Heliograph tripods.
The tripods are similar in all respects, the screw of either threading into the mirror bar or screen frame. Each tripod is provided with a hook at the base of the head, allowing the suspension of a weight when great stability is required.
Assembling.—There are two ways of assembling the heliograph and the position of the sun is the guide in determining which of the twoshould, in any given case, be employed. When the sun is in front of the operator (that is, in front of a plane through his position at right angles to the line joining the stations) the sun mirror only is required; with the sun in rear of this plane both mirrors should be used. With one mirror the rays of the sun are reflected directly from the sun mirror to the distant station; with two mirrors, the rays are reflected from the sun mirror to the station mirror, and thence to the distant station.
With one mirror: Firmly set one of the tripods upon the ground; attach the mirror bar to the tripod; insert and clamp in the sockets the sun mirror and sighting rod, the latter having the disk turned down. At a distance of about 6 inches, sight through the center of the unsilvered spot in the mirror and turn the mirror bar, raising or lowering the sighting rod until the center of the mirror, the extreme point of the sighting rod, and the distant station are accurately in line. Firmly clamp the mirror bar to the tripod, taking care not to disturb the alignment, and turn up the disk of the sighting rod. The mirror is then moved by means of the tangent screws until the "shadow spot" falls upon the paper disk in the sighting rod, after which the flash will be visible at the distant station. The "shadow spot" is readily found by holding a sheet of paper or the hand about 6 inches in front of the mirror, and should be constantly kept in view until located upon the disk. The screen is attached to a tripod and established close to, and in front of, the sighting disk, in such a way as to intercept the flash.
With two mirrors: Firmly set one of the tripods on the ground; clamp the mirror bar diagonally across the line of vision to the distant station; clamp the sun mirror facing the sun to one end of the mirror bar and the station mirror facing the distant station. Stooping down, the head near and in rear of the station mirror, turn the sun mirror by means of its tangent screws until the whole of the station mirror is seen reflected in the sun mirror and the unsilvered spot and the reflection of the paper disk accurately cover each other. Still looking into the sun mirror, adjust the station mirror by means of the tangent screws until the reflection of the distant station is brought exactly in line with the top of the reflection of the disk and the top of the unsilvered spot of the sun mirror; after this the station mirror must not be touched. Now step behind the sun mirror and adjust it by means of the tangent screws so that the "shadow spot" falls upon the center of the paper disk on the station mirror. The flash will then be visible at the distant station. The screen and its tripod are established as described in the single mirror assembling.
Alternate method with two mirrors: Clamp the mirror bar diagonally across the line of vision to the distant station, with the sun mirror and the station mirror approximately facing the sun and distant station, respectively.
Look through small hole in sun mirror and turn the station mirror on its vertical and horizontal axes until the paper disk on the station mirror accurately covers the distant station.
Standing behind sun mirror, turn it on its horizontal and vertical axes by means of the tangent screw attachments until the shadow spot falls upon the paper disk on station mirror.
Adjustment.—Perfect adjustment is maintained only by keeping the "shadow spot" uninterruptedly in the center of the paper disk, and as this "spot" continually changes its position with the apparent movement of the sun, one signalman should be in constant attendance on the tangent screws of the sun mirror. Movement imparted by these screws to the mirror does not disturb the alignment, as its center (the unsilvered spot) is at the intersection of the axes of revolution. Extra care bestowed upon preliminary adjustment is repaid by increased brilliancy of flash. With the alignment absolutely assured and the "shadow spot" at the center of the disk, the axis of the cone of reflected rays is coincident with the line of sight and the distant station receives the greatest intensity of light. Remember the distant observer is unquestionably the better judge as to the character of the flash received; and if therefore, adjustment is called for when the "shadow spot" is at the center of the disk, the alignment is probably at fault and should be looked after at once. In setting up the tripods always see that the legs have a sufficient spread to give a secure base and on yielding soil press firmly into the ground. Keep the head of the tripod as nearly level as possible and in high wind ballast by hanging a substantial weight to the hook. See that the screen completely obscures the flash; also that the flash passes entire when the screen is opened. This feature of the adjustment is partially regulatedby the set screw attached to the screen frame. The retractile spring should sharply return all the leaves of the screen to their normal positions when the key is released. Failure to respond promptly is obviated by strengthening or replacing the spring.
Operation.—It is of the utmost importance that uniformity in mechanical movement of the screen be cultivated, as lack of rhythm in the signals of the sender entails "breaks" and delay on the part of the receiver. Dark backgrounds should, when practicable, be selected for heliograph stations, as the signals can be most easily distinguished against them.
To find a distant station, its position being unknown, reverse the catch holding the station mirror and with the hand turn the mirror very slowly at the horizon over the full azimuth distance in which the distant station may possibly lie. This should be repeated not less than twice, after which, within a reasonable time, there being no response, the mirror will be directed upon a point nearer the home station and the same process repeated. With care and intelligence it is quite probable that, a station being within range and watching for signals from a distant station with which it may be desired to exchange messages, this method will rarely fail to find the sought-for station.
The exact direction of either station searching for the other being unknown, that station which first perceives that it is being called will adjust its flash upon the distant station to enable it when this light is observed to make proper adjustments. If the position of each station is known to the other, the stationfirst ready for signaling will direct a steady flash upon the distant station to enable the latter to see not only that the first station is ready for work, but to enable the distant station to adjust its flash upon the first station.
Smoked or colored glasses are issued for the purpose of relieving the strain on the eyes produced by reading heliograph signals.
Care of apparatus.—Minor parts of the instrument should be dismounted only to effect repairs, for which spare parts are furnished on requisition. Steel parts should be kept oiled and free from rust. Tangent screws and bearings should be frequently inspected for dust or grit. Mirrors should invariably be wiped clean before using. In case of accident to the sun mirror, the station mirror can be made available for substitution therefor by removing the paper disk. If the tripod legs become loose at the head joints, tighten the assembling screws with the screw-driver.
Powers and limitations of the heliograph.—Portability, great range, comparative rapidity of operation, and the invisibility of the signals except to observers located approximately on a right line joining the stations between which communication is had, are some of the advantages derived from using the heliograph in visual signaling.
The principal disadvantage results from the entire dependence of the instrument upon the presence of sunlight. The normal working range of the heliograph is about 30 miles, though instances of its having attained ranges many times greater than this are of record. The heliograph can be depended upon to transmit from five to twelve words per minute.
The signal lantern is an instrument designed for the purpose of transmitting signals by means of intermittent flashes of artificial light. It is the standard night visual signaling equipment furnished by the Signal Corps and depends for its illumination upon the combustion of acetylene gas.
Acetylene.—Acetylene is a pure hydrocarbon gas, producible in various ways, the commoner of which are: (a) By dropping calcium carbide into water; (b) by dropping water upon calcium carbide. This gas gives, when burning, high penetrative power, and was first described by Mr. Edmund Davy, professor of chemistry to the Royal Dublin Society, in 1836.
Calcium carbide.—In the manufacture of calcium carbide for commercial purposes the best quality of coke and quicklime are used. These two substances are powdered thoroughly, mixed in proper proportions, and then placed in an electrical furnace. Under the action of the intense heat (5,500° F.) these two refractory substances unite and form calcium carbide. Calcium carbide is of a grayish-white color, crystal in appearance, and is nonexplosive and noncombustible, being, except for its affinity for water, an absolutely inert substance. A pound of commercial carbide will produce approximately 5 cubic feet of gas. When water is brought in contact with calcium carbide, the generation of acetylene is rapid; owing to its strong affinity for water it will become air slacked and slowly lose its strength if exposed to the action of the moisture in the atmosphere; consequently, when stored or being transported it should be kept in air-tight cans.
When calcium carbide is brought in contact with water, the following occurs:
As is known, the principal components of water are oxygen and hydrogen, and calcium carbide is calcium and carbon. When brought in contact, the oxygen in the water decomposes the calcium in the carbide, and in this decomposition the hydrogen in the water is liberated and unites with the carbon of the carbide, forming a hydrocarbon gas which is acetylene. It is a pure white light of intense brilliancy and high candlepower. The spectrum analysis of acetylene shows that it is almost identical with sunlight, and in consequence delicate shades of color appear according to their true value as under the light of the sun, consequently it penetrates fog to a greater distance than other lights. Acetylene is like other gases—explosive when mixed with air in proper proportions, confined, and ignited—and the same precautions should therefore be taken in its use as would be in the handling of coal or water gas, gasoline vapor, etc. As acetylene is very rich in carbon, it will not burn in its pure state without smoking. To avoid this, burners have been constructed so that the gas is mixed with the proper proportion of air at the burner tip, to insure perfect combustion. The burners for acetylene are different from those for other gases. In order to get a flat flame, the gas is brought through two perfectly round holes at an angle which causes the two flames to impinge upon each other and thus form a flat flame.
Method of gas generation.—The method employed for producing acetylene in the signal lantern is by bringing water into contact with calcium carbide.The disadvantage of this method is that when the water is not in excess and does not entirely surround and touch each piece of carbide the heat of generation will so change the chemical properties of the gas that combustion at the burners is not satisfactory.
This change is technically known as "polymerization," or the breaking up of acetylene into other hydrocarbons, such as vapors of benzine, benzole, etc. These form a tarry substance which is apt to condense at the burner tip and clog the openings. Also they deposit carbon on the burners, as they require more air for perfect combustion than does pure acetylene. Another disadvantage of this system is that after the carbide and water are in contact, generation of gas will continue until all the water is absorbed. Where, however, portability of the generating apparatus is desired and resort to this method is necessary, the objections are not important, if the apparatus is well constructed and care is taken in its use.
Description.—This equipment consists of a signal lantern with cartridge generator attached. The lantern is equipped with a special aplanatic lens mirror, 5 inches in diameter and about 3 inches focus. The lantern is packed complete in a wooden case with shoulder straps and the following extra parts are included, each part having its own receptacle in the case: 2 burners; 1 cover glass; 3 cartridges of calcium carbide of 5 ounces each; 1 pair of gas pliers; 1 tube white lead; 1 extra filter bag; 1 screw-driver.