Signal (signaling)

“ The correct determination of background color from the vicinity of home stations is usually difficult and unsatisfactory, and it is considered the best method to establish communication with the distant station by simultaneously using several kinds of signaling apparatus, that kind producing the most intelligible signals being retained for continued use. ”

“ 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. ”

“ 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. ”

“ The assignment of men should be such that a continuous watch for signals is kept and the responsibility for neglect to promptly answer calls determined. Of the station men, one is the sender, whose duty it is to transmit all signals to contiguous stations. Another, the receiver, attends the telescope and reads and calls off the signals displayed at the distant station. A third man acts as recorder, alternately calling off the outgoing message to the sender or transcribing the incoming message repeated by the receiver. ”

“ It is time gained to do so; it is a loss of time and an annoyance to run letters together. Nothing so distinguishes the good from the indifferent operator, visual or telegraph, as this. When signals are being made with a flag, a fraction of a second will be ample. In using the lantern or heliograph, the pause between letters should be relative to the time of display of the elements, longer than with the flag. To prevent any entangling of the flag upon its staff, skillful handling, acquired by practice, is necessary. ”

“ When recourse to any method of sight signals can not be had on account of weather conditions or lack of suitable apparatus, sound signals may often be advantageously used. The commoner means of furnishing sound signals are the horn and the whistle, though many other kinds of apparatus are practicable. The necessary elements of any system can be indicated by one short, two shorts, and a long blast. ”

“ 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. ”

“ The visible signal is better adapted to lines in which the signaling is done by means of direct current, as, for example, in systems where the removal of the receiver from the hook at the subscriber's station closes the line circuit, causing current to flow through the winding of the visible signal and so displaying it until the receiver has been hung upon the hook or the circuit opened by some operation at the central office. ”

“ E. Price-Edwards recently delivered before the Society of Arts a valuable lecture on "Signaling by Means of Sound," in which he considered the requisites of a good signal, and discussed the merits of the different signals in use. The essential quality of a good sound signal is that it shall give a strong sound which can be uniformly heard at a definite distance. The range of a sound is determined by the force with which it is uttered, and is modified by certain conditions of the atmosphere. ”

“ They should never be abandoned until every device has been exhausted, and they should be renewed and continued at different hours of the day and night. It must be remembered that efforts which have failed because the observer's attention has been drawn in another direction may at any other moment be successful if the observing glass chances to bear on the calling signals.
During the whole time that signals are being made to attract attention the calling station must watch closely with the telescope the station called. ”

“ To find a signalman near any known station, note with the unaided eye some prominent landmark near which the looked-for person or object is supposed to be, and direct the telescope upon the place, as sight is taken over a gun barrel, covering the object; if the eye is now placed at the eyeglass of the telescope, the prominent or directing landmark will be found in the field of view. ”

“ 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 Ardois system is a special system of night signaling designed to utilize combinations of red and white signal lights in forming the elements of any desired alphabet. Four signal lamps capable of displaying either red or white lights are attached at convenient intervals to a vertical cable or staff rigged between the top of a mast and the deck, if on shipboard, or the ground, if on shore. Illumination is furnished by electrical means and any desired combination of lights is automatically obtainable by operating a keyboard. ”

“ When a signal station is to communicate with two or more stations, a telescope should be firmly fixed bearing on each, when practicable, and so far apart that those communicating with one station will not disturb the other party. ”

“ Light: The light of a field glass is expressed by a number which is the ratio of the amount of light which reaches the eye through the glass to the amount which enters the eye unaided. This comparison will be reached by means of the absorption apparatus [130] furnished by the Signal Corps. This apparatus consists of two wedge-shaped vessels made of brass with glass windows in the sides, and are filled with a perfectly black liquid. The sky line is first viewed through the apparatus with the naked eye and the instrument adjusted to limit of visibility. ”

“ Visual signaling is and always will be a most valuable means of transmitting information [10] in 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. ”

“ The white flag will be used against dark and the red against sky or broken backgrounds. The distant station is the better judge as to which color flag is best suited to given conditions and the color indicated by it should invariably be used. For night signaling, the acetylene lantern is usually employed. Long-range night signaling should be done with the searchlight if available. The employment of the semaphore, in daytime, and the Ardois system, at night, will be confined to more or less permanent stations. ”

“ Each and every operator will also have a personal signal of like character. Station calls or personal signals when once given or assumed will not be changed except by order of higher authority. Every station should at all times have on hand a list of all calls and personal signals liable to be encountered in station working. The general call suited to attract the attention of any station whose regular call is unknown [79] will always be a signal represented by the letter "A" in the Morse or the letter "E" of the Army and Navy Code. ”

“ Backgrounds of this description do not accord with either of the essential requirements of the signal station and should be avoided whenever possible.
In general, sky backgrounds should always be selected for signal stations when conditions are such that the requirement of secrecy can be dispensed with; if, on the other hand, there is reason to fear that the signals may be intercepted by the enemy, dark backgrounds [71] should invariably be chosen, even though the disadvantages they impose, render them less desirable visually. ”

“ Signal stations should be convenient for messenger service and hence as near commonly traveled roads as the physical contour of the country will permit. Locations for signal stations should be so selected that the visual lines do not cross traveled roads, camps, etc., as dust and smoke in the daytime and lights at night are factors in determining the visibility of signals. Signal stations can if necessary be artificially concealed by erecting screens constructed of limbs of trees, etc., about the flanks and rear. Sheltered positions should be utilized in windy weather. ”

“ The force may not be strong enough for an uninterrupted watch. To provide, so far as possible, for this contingency, it may be concerted that if communication is required at unusual time, or is of pressing importance, certain flags shall be displayed, rockets discharged, smokes shown, or other attention-compelling signals used. ”

“ The power of a telescope or a field glass can more accurately be measured by means of a dynameter, which is a microscope which can be fitted over the eyepiece end of the instrument, and which magnifies the image. ”

“ If more than 10 powers are desired, a holder becomes necessary, and if the holder is intended to be portable a greater power than 50 is not practicable, as the movement of the air or the slightest touch of the hand sets up vibrations that render clear vision impossible. ”

“ If a glass should be broken and an extra one is not available to replace it, signaling can be continued by turning the flame on full and using the heliograph shutter, [35] a cap or piece of board in front of the lantern to obscure and reveal the flash. Without the protection of the cover the flame is easily blown out when turned low, but will not be extinguished even in a strong wind if the gas is turned full on. ”

“ Definition.—The term "field message" is applied to all messages sent over field lines of information. All field messages for transmission over field lines of information by electrical or visual means should be plainly written by the sender on the blank forms in the United States Army Field Message Book. The practice of verbally delivering telegrams to enlisted men for transmission should invariably be discouraged. ”

“ The capability of the instrument, however, is thereby much limited; great powers give plain images only with relatively long tubes; glasses must be held the steadier the more they magnify; and with increasing power all vibrations become more troublesome and render minute observations very difficult or impossible. ”

“ Brass shells are used and are packed in boxes colored to indicate the character of stars employed in loading. The color of the star fired may indicate an element of any alphabet or any special signal which may be desired. The stars rise to a height of about 200 feet and remain visible for some time. ”

“ Dark backgrounds are far more common and more easily obtainable than sky exposures. They afford the maximum means of concealment from hostile observation, but materially reduce the range, speed, and accuracy of signal transmission. ”

“ 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. ”

“ 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. ”

“ Sample.—The bidder shall furnish with his proposal a sample of the glass which he will supply, and award will be made after comparison of the samples with models on file in the office of the Chief Signal Officer. The maker will be allowed to examine the model glasses in detail in the office of the Chief Signal Officer of the Army, Washington, D. C.
3. Inspection and test.—When the order under this specification is complete, the contractor will notify the Chief Signal Officer of the Army, who will cause an inspection to be made. ”

“ He will enter in the proper places, at the head of the blank, the number of the message, the call letter of his station, with his personal signal, the check (number of words or groups of cipher contained in message, counting address and signature) , and, after "OK" has been received, he will enter the time the message was sent, and the call letter of the receiving station, with the personal signal of the receiving operator.
Order of transmission.—To transmit a message, the operator will send: (1) The number of message and call letter of his station; (2) his personal signal; (3) the check ”