photograph: tripodFig. 4.—The signal lantern.
Fig. 4.—The signal lantern.
The lantern is made of brass, all parts of which are riveted. The burner is of the double tip form, consuming three-quarters of a cubic foot per hour. Thelantern is fitted with a hood to provide proper ventilation and at the same time to prevent the flickering of the light by the wind. The front door of the lantern is hinged and fastens with a spring clasp; it is so arranged that it can be entirely removed if necessary. The cover glass is made in three sections and is not affected by the expansion and contraction of the metal due to changes in temperature. The glass is fastened by the aid of a spring wire, so that it can be readily removed if it is necessary to replace a broken section. In the base of the lantern is a key and the adjustment for regulating the height of the flame. The key is so arranged that when not depressed but little gas is admitted through the by-pass to the burnerand the flame is low. By depressing the key as much gas as can be entirely consumed is admitted to the burner, which gives a bright flash. At the back of the lantern there is an adjustable handle, so that the equipment can be used as a hand lantern if desired. This form of lantern can be used with the regular heliograph tripod, the generator being either attached to the back of the lantern or suspended, as shown infigure 4. When practicable it is better to attach the generator to the lantern, as shown infigure 5. The candlepower of this lantern is about 1,900.
photographFig. 5.
Fig. 5.
The generatorused is known as "the cartridge generator," and while constructed on the water-feed principle, the disadvantages incident to this method are eliminated as far as possible. It is constructed of brass and has a removable top. Attached to the inside of the top is a flexible frame with a spring latch, the spring latch being hinged. (Fig. 8.) At the top of the frame is a tube or cylinder, the bottom of which is conical in shape and covered by a rubber plug. At the bottom of the frame is a hollow tube, which is the water inlet. The cartridge proper consists of a tin cylinder, having an opening at either end. A small cylinder of wire mesh extends from and connects theseopenings. The carbide lays around this mesh on the inside of the cartridge. The rubber plug before mentioned fits into the upper opening, and the water tube into the lower opening. (Seefigs. 7,8, and9.) Inside the tube, at the top of the frame, is a filter, the function of which is to remove the dust and moisture from the gas. The outlet from this chamber is by a brass bent tube having a stopcock attached thereto.
Figure 6gives a sectional view of the generator with the cartridge in place.D F G Hrepresent the valve frame andIthe cartridge attached. The reservoirAis filled with water, and when the frame is immersed, with the valveRclosed, the air contained in the cartridge and tubing can not escape, the water seal preventing, while the confined air prevents the water from rising in the tubeN. When the valve atRis opened and the air is allowed to escape, part of the water from the reservoir rises into the tubeNand then out through the small holeOto the carbide. Gas is immediately generated, the pressure of which prevents further ingress of the water from the tubeN, and the generation of gas is suspended.
As the gas passes out through the valve atRthe pressure decreases, permitting the water to again rise in the tube and flow throughO. Gas is again generated, which at once exerts its pressure and cuts off the supply of water. This is the automatic action by which water is brought in contact with the calcium carbide. Thus it will be observed that the use or escape of the gas regulates the generation by the simple device of the rise and fall of a water column. There is a capMscrewed over the tubeN. This isused to deflect the course of the water downward, so that the carbide in the lower part of the cartridge is first attacked. There is a needle inside of capM, which can be used for cleaning the holeO. When the gas is generated it passes through the filterDon its way to the burner throughR. This filter consists of a tube loosely packed with ordinary nonabsorbent cotton, which should never cover the escape pipe leading to the valveR. In passing through this cotton filter moisture and dust are removed from the gas. In the latest model a felt filter is used instead of cotton.
Fig. 6.—Signal lantern generator.
Fig. 6.—Signal lantern generator.
The escape pipeFprovides a means for the escape of gas generated and not used or generated more rapidly than consumed. Should an excess be generated, it passes down through the tubeF, and, finding its way through some small holes in the bottom of this tube, escapes through the water seal and the opening atC. It will be noted that if escaping gas atCshould become accidentally lighted, the flame can not strike back into the filter and cartridge because of the water seal. Theprincipal things to observe in the operation of this generator are the following:
(1) To see that the rubber plugsfit tightlyinto the openings of the cartridge.
(2) That the tubeN, the capM, and water holeOare not stopped up.
(3) That the cotton in the filter is changed frequently.
(4) That thestopcock R is closed before inserting the frame in the water. If this latter instruction is not complied with, it can be readily seen that the water will have free access to the carbide and excessive generation will occur.
When the charge is exhausted, the entire cartridge is taken out and thrown away. This eliminates the handling of carbide and the disagreeable task of cleaning out the residuum after the gas has been extracted.
Connection is made from the stopcockRto the hose connection on the lantern proper, and this is the passageway of the gas from the generator to the burner. As soon as the stopcock is opened the water rises through the tube and flows to the carbide. The advantage of the cartridge being submerged in the water is to reduce and absorb as much of the heat liberated by generation as is possible. These lanterns have been tested up to a distance of 10 miles with the naked eye, and under favorable conditions can be used over a range somewhat in excess of this. With a 30-power telescope the flash can be read at a distance of 30 miles.
Operation and care.—Take the lamp and generator from the case by aid of the handle attached to thelamp; screw the complete outfit on a heliograph tripod, or stand the outfit on a level object; remove the cover of generator, to which is attached the flexible frame (fig. 9); detach spring from the catch of the flexible frame; tear off flaps from the ends of carbide cartridge (or pry off small caps) and attach the cartridge as shown infigure 9. Then attach to frame as shown infigure 10, being careful to see that both rubber plugs fit tightly into the holes in the cartridge; fasten the latch of the spring over the metal catch; close stopcockRon service pipe; completely fill the outer can of generator with water, the object being to have the generator level full of water when the lamp is in service, then immerse the frame and cartridge, pressing the top of the generator down tight. In doing this the water will overflow the sides of the generator tank. Now connect by rubber tubing the stopcock with the gas inlet at the bottom of the lamps, as shown infigure 4; then (1) open front door of the lamp, (2) light a match, (3) open stopcock, and (4) light the gas at the burner. In doing this hold the key open. In the new model the key and hose connection are on the side of bottom of lamp.
When the gas is ignited, the lamp is ready for signaling, and the key can be operated as is the Morse telegraph instrument, but of course not so rapidly.
In the event of the flame being too high when the key is closed, adjustment can be made by loosening the set screw (fig. 4, indicated by an arrow) and adjusting the light by turning screwb. When at the proper height, tighten the set screw which locks the by-pass in its proper position. In the new model this isaccomplished by aid of the regulator by-pass valve at the left-hand side of bottom of lamp. The lamp is properly adjusted when shipped and should not be changed unless absolutely necessary. Connect the rubber tube to the burner before opening the stopcock on the generator.
To recharge the generator, take the frame and the old cartridge from the case, throw away the old case and replace with a fresh one, proceeding as before. See that fresh water is put in the generator each time a new cartridge is used.
photographFig. 7.
Fig. 7.
In the tube through which the service pipe passes is a felt filter for taking the dust out of the gas. If the filter clogs, unscrew the cap to which the service pipe is attached, clean the felt, or replace it with a new filter, binding it in place by a stout thread or string.
If the burner of the lamp does not produce a perfectly flat flame it has become clogged and should be cleaned with the burner cleaner furnished, or a new burner should be substituted, care being taken to put a little white lead on the nipple, if practicable, so as to insure a tight joint.
In repacking the outfit in the case, throw out the water and wipe the can and generator parts dry. You can not be too careful to keep the apparatus clean. This is especially true of the small pipe that passes up through the bottom of the cartridge, with a cap over it. The cap should always be screwed in place, as its object is to prevent the water from squirting to the top of the cartridge.
photographFig. 8.
Fig. 8.
Fig. 9.
Fig. 9.
The back of the lamp can be removed by turning the small thumbscrew on the top and drawing out the pin which holds the shell into which is fitted the lens. It is not necessary to take the back out except to replace a lens, as the latter can be cleaned by opening the front door.
If it is desirable to use the lamp as a hand lantern the flame can be turned on full by turning the button in a vertical position; this locks the key open. In the new model depress the key and lock it with the latch above the key.
One charge of calcium carbide will supply gas to burn about one hour with the light turned on full, or for approximately three hours' signaling.
Fig. 10.
Fig. 10.
If signaling is to be suspended for some hours, empty the water out of the generator and close valveR.
The glass front can be replaced by taking out the wire spring. The glass cuts should be mounted in a horizontal position and, to prevent breaking, should be protected from rain when the lamp is hot. 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,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.
Old model lamps are serially numbered from 1 to 200, inclusive; the new model lamps are serially numbered from 201 upward.
Powers and limitations of the acetylene signal lantern.—As conditions are usually more uniform at night than in the daytime, the signal lantern is probably the most reliable of all visual signaling outfits. The advantages of this form of apparatus are its portability, speed of operation, and comparatively great range. The principal disadvantages are due to the interference caused by rain, fog, and moonlight. The speed attainable with the lantern is about the same as that attainable with the heliograph.
Two distinct kinds of rockets and shells are issued, one of which is adapted to day and the other to night signaling. Shells and rockets of the amber smoke type with parachutes are used in the daytime, while shells (red and white) and sequence rockets are used at night.
photographFig. 11.—Signaling rocket and accessories.
Fig. 11.—Signaling rocket and accessories.
photographFig. 12.—Signaling shells.
Fig. 12.—Signaling shells.
Description.—The shells are all single shot and are fired from a 5-inch portable mortar, attaining a height of about 550 feet. The report of explosion can be heard at varying distances up to 5 miles, depending on weather conditions. The parachute attached to the smoke shell suspends a small light wooden tubewhich, after ignition, emits smoke for from four to six seconds. The red and white shells, on bursting, discharge a shower of red and white fire which can be observed for some time, in fact almost until the sparks fall to the ground.
Rockets for both day and night signaling are equipped with parachutes. The smoke rocket is of similar construction to the smoke shell. The sequence rocket is so arranged at the base that threaded sections of combustible material burning either red or white can be attached to it. Rockets ascend about 700 feet.
Each rocket and shell is supplied in a cylindrical sealed tin can, which also contains a port fire, wind matches, and for the rockets a stick in four sections. On the outside of the can is a label designating the kind of shell or rocket therein contained. These cans are easily opened by pulling a ring and require no special opening tool.
Operation.—In firing shells the mortar should be surrounded by earth or sand, preferably placed in sacks. The fuse for all shells is very rapid and should be ignited by attaching the port fire to a long stick.
All of the old type Signal Corps mortars, originally designed to withstand a pressure of 1,000 pounds per square inch, and made of ordinary iron pipe, are considered unsafe and should be immediately destroyed. The new mortars, recently made for the Signal Corps by the Ordnance Department, are of cold-drawn steel having a tensile strength of 6,000 pounds per square inch, which is more than the maximum pressure for firing any of the Signal Corps bombs. They arestamped "Signal Corps, U. S. A., Model 1907," or "Rocket Gun, Watertown Arsenal, 1907."
The sequence rocket is prepared for use by attaching red or white sections to the base in such a combination as to form letters of the alphabet which it is desired to use. Letters containing the same color in sequence are very difficult to read and should be avoided whenever possible. If necessary to use them, blank sections furnished for the purpose should be inserted between the units. The base of the rocket will secure six units.
When rockets are to be fired the sticks must be firmly attached, the rocket placed upright in a trough, upon a frame, or against a post. If the fuse is beneath the paper covering the "choke" orifice, the paper should be torn off and the rocket ignited by a port fire. In the rockets now used the fuse extends through the covering and can be lighted direct. If the night be damp this fuse should be exposed only a moment before the rocket is fired. If several rockets are to be fired in succession it is well to prepare them all at the same time, and to have them all stood upright, but each separated from the other at a distance of at least 6 feet, else one may ignite the other accidentally. In firing for chronosemic signals, one rocket ought to be kept ready upon the frame and in reserve, to be fired in place of one that fails.
If a rocket misses fire it is to be taken from the stand and laid on the ground. Its place is at once supplied by a similar rocket, fired in its stead. The failing rocket is laid on the ground pointed away from the station in order that if it has only hung fire andshould afterwards ignite it may not disarrange the signal shown or injure any one of the party. If the wind blows freshly the rocket to be fired should be inclined slightly against the wind.
Signal rockets and shells are furnished in sealed cans and should not be removed therefrom until ready for use. Strict economy should be observed in the use of these articles and on no account should they be used for purposes of display.
Employment.—Rockets and shells are especially valuable in making preconcerted or emergency signals. On account of the great amount of ammunition required it is impracticable to spell out messages with them. These articles should be supplied to outposts, detached stations, etc., to be used for signaling the approach of the enemy or the happening of unexpected events, the necessity for promptly knowing which is important.
If signal stations are to be permanently occupied, and it is impracticable to electrically connect them, communication may be facilitated by erecting semaphores.
Semaphores, while primarily used for day signaling, can be advantageously used at night by attaching lights to the arms.
The navy semaphore consists of four arms pivoted at the ends, three on one side of the upright, or pole, and one on the other side. These arms have three positions: Horizontal; upward at an angle of 45° to the horizontal; downward at an angle of 45° to the horizontal.
Full instructions for the operation of the semaphore, and also for the use of balls, cones, drums, pennants, and whefts as distant signals, are given in the International Code of Signals.
The electric searchlight, when available, can often be successfully employed for night signaling, frequently affording efficient means of communication between ships and shore stations, when wireless working is impracticable. This system of visual signaling is practicable and especially valuable where the stations are, on account of the terrain, not intervisible.
Methods of employment.—In signaling with the searchlight the usual method of handling the shaft or beam is identical with that employed with the flag. In the first position the beam is shown vertically, while motions to the right, the left, and directly serve to indicate the elements of the alphabet. Chronosemic signals may also be used in searchlight signaling, the shaft of light being directed intermittently on some conspicuous object, such as a cloud, balloon, or high mountain top.
These signals are pyrotechnic compositions which burn with great intensity of light and color. The colors red, white, and green are found best suited for signaling. The signals are prepared in the form of cartridges and are burned from a holder. The colors burned may indicate the elements of any alphabet, or such other special signals as may be desired.
The Very system employs projected red, white, and green stars, which are shot from pistols held in the hand.
Description.—The Very pistol is a breechloading, single-shot pistol with an 8-inch steel barrel chambered to receive a 12-gauge commercial shotgun shell. 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.
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.
This system is valuable on vessels or at permanent shore stations, but the great expense of installation precludes its general use. Wiring diagrams and technical instructions relative to this apparatus are in all cases furnished when the same is issued.
flare gun photographFig. 13.—The Very pistol.
Fig. 13.—The Very pistol.
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. The advantage of this system of signaling is that it can be used in any kind of weather, both in daytime and at night. On the other hand, sound signals are generally more difficult to read than sight signals and tend to disclose the presence of stations to hostile forces.
The object of this chapter has been to describe only the standard visual signaling equipment issued and generally utilized. Besides the methods detailed, there are many others which may be successfully employed by the ingenious signalman when the necessity for them arise. The use of any means of transmitting signals whatever is justifiable when for any reason the regular apparatus is not available. Special conventional scout signals are given in paragraph 82, Field Service Regulations.
In the field many instances will occur where it will be necessary to transmit information rapidly without recourse to the authorized equipment. This will be especially true of outposts, detached stations, patrols, and other small bodies of troops, and it will devolveupon individual commanders to improvise methods of signaling best suited to the occasion and the conveniences at hand.
ALPHABETS OR SYSTEMS OF SIGNALS.
AMERICAN MORSE.CONTINENTAL MORSE.ARMY AND NAVY.Letters—A- —- —22B— - - -— - - -2112C- - -— - — -121D— - -— - -222E--12F- — -- - — -2221G— — -— — -2211H- - - -- - - -122I- -- -1J— - — -- — — —1122K— - —— - —2121L——- — - -221M— —— —1221N— -— -11O- -— — —21P- - - - -- — — -1212Q- - — -— — - —1211R- - -- — -211S- - -- - -212T——2U- - —- - —112V- - - —- - - —1222W- — —- — —1121X- — - -— - - —2122Y- - - -— - — —111Z- - - -— — - -2222&- - - -tion1112Numerals—1- — — -- — — — —11112- - — - -- - — — —22223- - - — -- - - — —11124- - - - —- - - - —22215— — —- - - - -11226- - - - - -— - - - -22117— — - -— — - - -12228— - -- - — — — - -21119— - - —— — — — -12210———— — — — —2112Punctuation—. Period- - — — - -- - - - - -: ColonKo— — — - - -; SemicolonSi— - — - — -, Comma- — - —- — - — - —-? Interrogation— - - — -- - — — - -! Exclamation— — — -— — - - — —Fraction line-- HyphenHx— - - - - —' Apostrophe- — — — — -£ Pound Sterling— - — - -() ParenthesisPn— - — — - —" Quotation marksQn- — - — - — - —Paragraph— — — —BracketsBnDollar markSxDashDxUnderlineUx
The following abbreviations, conventional signals, and code calls are authorized in visual signaling:
aafter.bbefore.ccan.hhave.nnot.rare.tthe.uyou.uryour.wword.wiwith.yyes.
International Code useICU(Navy) telegraph dictionary useTDU(Navy) geographical list useGLU(Navy) general signal useGSUNavy list useNLUVessel's numbers useVNUCipher "A" use[a]CAUCipher "B" use[a]CBUCipher "C" use[a]CCU
FOOTNOTE:[a]These calls are for preconcerted use in or with the navy.
FOOTNOTE:
[a]These calls are for preconcerted use in or with the navy.
[a]These calls are for preconcerted use in or with the navy.
Although the use of but one alphabet is authorized in visual signaling in the U. S. Army, emergencies may arise where it may be imperative to use either the Army and Navy, the Continental Morse, or the American Morse alphabet. Instructions for the use of either alphabet under such conditions are given.
THE ARMY AND NAVY ALPHABET.SIGNALING WITH FLAG OR TORCH, HAND LANTERN, BEAM OF SEARCHLIGHT, AND HELIOGRAPH.
There is one position and three motions. The position is with the flag or other appliance held vertically, the signalman facing directly toward the station with which it is desired to communicate, his body erect and feet sufficiently separated to insure stable equilibrium. The first motion ("one" or "1") is to the right of the sender, and will embrace an arc of 90°, starting with the vertical and returning to it, and will be made in a plane at right angles to the line connecting the two stations. The second motion ("two"or "2") is a similar motion to the left of the sender. The third motion ("front," "three," or "3") is downward directly in front of the sender and instantly returned upward to the first position.
The beam of searchlight will be ordinarily used exactly as the flag, the first position being a vertical one.
To use the torch or hand lantern, a footlight must be used as a point of reference to the motion. The lantern is more conveniently swung out upward to the right of the footlight for "1," to the left for "2," and raised vertically for "3."
In using the heliograph, the first position is to turn a steady flash on the receiving station. The signals are made by short and long flashes. Use short flashes for "1," two short flashes in quick succession for "2," and a long, steady flash for "3." The elements for a letter should be slightly longer than in sound signals.
Each word, abbreviation, or conventional signal is followed by "3."
The full address of a message is considered as one sentence and will be followed by the signal "33."
The signal to indicate that "cipher follows" and "cipher ends" is with the flag and torch "XC3," and with other methods, except the International Code, by "XC." It will always precede and follow a cipher message or such part of a plain text message as is enciphered.
The following conventional signals are authorized in the use of the army and navy alphabet:
End of a word3End of a sentence33End of a message333Numerals follow (or) numerals endxx3Signature followssig. 3Error12 12 3Acknowledgment (or) I understand22 22 3Cease signaling22 22 22 333Cipher follows (or) cipher ends2122 121 3Wait a moment1111 3Repeat after (word)121 121 3 22 3 (word)Repeat last word121 121 33Repeat last message121 121 121 333Move a little to the right211 211 3Move a little to the left221 221 3Signal faster2212 3
TO SIGNAL WITH THE FLAG, TORCH, HAND LANTERN, OR BEAM OF SEARCHLIGHT.
The dot is made by a motion to the right of the sender embracing an arc of 90°, starting from the vertical and returning to it, in a plane at right angles to the line connecting the two stations.
The dash is made by a similar motion to the left.
The space which occurs only between dots is made by prolonging the signal for the last dot for an interval of time equal to the time of an additional dot, the staff of the flag, the beam of the searchlight, etc., being maintained in a horizontal position for the time specified. The signal so made would therefore represent a dot and space.
The letter "C" is accordingly made thus: Right, right prolonged, right.
The long dash ("L") is distinguished from the short dash ("t") by prolonging the signal to the left for a period of time equal to one dot. The long dash representing "naught" is similarly made by prolonging the signal to the left for a period of time equal to two dots.
The "front" signal is made by lowering the flag from the vertical position to the front and immediately returning it to the vertical position.
A slight pause is made between each signal.
The following conventional signals are authorized, using the Morse alphabets:
End of wordone front.End of sentencetwo fronts.End of messagethree fronts.
The dot is made by pressing down the key of the shutter and immediately releasing the same.
The short dash is made by pressing down the key and holding it down for a period equal to two dots.
The long dash ("L") is made by holding down the key for a period equal to three dots while the longer dash (naught) requires the key to be held down for a period equal to four dots.
The space is made on the heliograph as in ordinary telegraphy by the absence of any signals for a period equal to the time of one dot.
On the heliograph the letter "C" is made as follows: Short flash, short flash, interval, short flash.
coloured flagsFig. 14
Fig. 14
coloured flagsFig. 15.
Fig. 15.
When the call of a station is acknowledged, both stations will adjust each on the flash of the other.When adjustments are satisfactory, the station called will acknowledge and cut off its flash, and the calling station will proceed with its message.
Description.—By means of the International Code of Signals people of different nationalities may communicate with each other, although neither party has knowledge of any language save his own native language. The code is, as its name indicates, international, and every seagoing vessel of every nation is equipped with its flags. The Code of Signals contemplates the use of 26 flags (figs. 14and15); one for each letter of the alphabet and a code pennant. Complete instructions relative to the use of this code are contained in a book issued by the Hydrographic Office, Navy Department, and known as the "The International Code of Signals." In using this system the signals are displayed by hoisting combinations of two, three, or four flags. All possible combinations represent words, expressions, or phrases, which may be found in the "International Code of Signals," referred to above.
Two-arm semaphore.—This system is frequently used by the United States Navy, the following instructions covering the use of the system:
1. To communicate with a station:
Face the station and wave the flags over the head to attract attention, making at frequent intervals the call letter of the station. When the station called is ready to receive the message, it answers by displaying its own call letter until the sender makes the"alphabetical" or "numeral," as the case may be. Then proceed with the message. At the end of each word bring the flags across the lower part of the body.
2. To call a ship:
Hoist International Code letter J and make code letter of ship; then proceed as in article 1.
3. To make a general semaphore signal:
Hoist cornet; all ships answer by answering pennant; then make signal.
4. At the end of the message extend the arms horizontally and wave the flags until the receiver answers in the same manner, showing that the message is understood.
Should the receiver miss a word, he signifies the fact by waving the flag over his head. The sender will then cease signaling and wave his flags similarly to show that he understands. The receiver then makes "repeat last word," or whatever he wishes to say.
Should the sender make a mistake, he will make the "error" signal until answered by the receiver with the same signal. He then proceeds with the message.
In using this system in connection with the Army and Navy Code, the red lamp indicates "1" and the white lamp "2." Four lamps are placed on a vertical staff and electrically illuminated to indicate the numerals of the Myer Code, which represents the letters of the alphabet. For instance, white-white, or "22," represents the letter "A," and white-red-red-white, or "2112," represents the letter "B," etc. In this system the lights indicating the letters of the alphabet are read from the top downward.
When the lamps are placed horizontally, they are read from the sender's right to his left, and consequently from the receiver's left to his right.
When the letters of the alphabet are to be used to indicate the meaning set opposite them in the following tabulation, the upper light of the display is pulsated. This is effected by means of a special pulsating key. Special signification is not given "I" and "T," they being represented by a single lamp.