Since a submarine has an eye to see with, it is both proper and fitting that it should have a tongue so that it may speak and ears so that it may hear. In fact, an undersea boat is almost human.
The early submarine, though, was not only as blind as a cave fish, but it was as deaf and as dumb as a snail; and since this was the case, it had to do whatever talking was necessary by means of a deaf and dumb alphabet, that is, by signaling with flags, or wigwagging, as it is called.
The Tongue and Ears of a Submarine.—The tongue of a submarine—or rather tongues, for it has several—is the fanciful name I have given to the means, methods, and schemes by which messages are sent from one submarine to another submarine or to shore, and the ears are the devices by which it receives messages from other submarines and from shore stations.
There are two conditions under which messages must be sent from and received by a submarine, and these are (1) when she is running light or awash, and (2) when she is running submerged.
Now, most of the signaling systems can be used only when the submarine is on the surface, and a couple of them can be used only when she is under water.
Then, again, some systems are good only for daylight signaling, and others for night signaling; others will cover very short distances, but there are systems that will send and receive over long distances. But whatever the system may be there will be found some weak point in it as far as the submarine is concerned.
Kinds of Signaling Systems.—Since no one signaling system will meet the rigid requirements of the submarine, several systems are used. When the craft is on the surface, these are: (1) the flag, or wigwag, system; (2) the flashlight system; and (3) the wireless telegraph system. When the submarine is under water the signaling systems used are: (1) the bell, or violin, system; and (2) the electric current system—all of these will be described in order and as we go along.
The Wigwag Way of Signaling.—The oldest way of sending messages at sea is by wigwagging, that is, using flags, and this system is still in use in the navies of all nations for close range daylight communication.
The way wigwagging is done is like this: Each craft has a signal book which gives the positions of the flags and the meaning of them. These flags are usually manipulated by a signalman (see Fig. 55) though sometimes a mechanical apparatus called a semaphore, which has two movable arms to hold the flags, is used.
Two flags are used, one in each hand or on each arm, and each position of the flags means a letter of the alphabet, and so by showing the flags in various positions to represent different letters words are spelled out.
Another scheme that is used to signal with flags is by running, that is displaying, a number of different colored flags on a halyard. The combinations of flags—or to use the right word, permutation, which means the number of different arrangements of a few flags that are possible—are numerous and each permutation represents some word or a sea-term.
Now, you might think that it would take a couple of hundred flags of different colors to represent a message, and, further, that since there are only eight colors which can be told from each other at a distance of half a mile, signaling by colors could not be done.
But this is what you think, and not what you have figured out, for if you have eight flags of different colors and display them, four at a time, on the signal halyard you can make the surprising number of 1680 permutations; and this, you will allow, is enough to say anything that you may have to say.
Although a code book is found in every signalman’s outfit, he is a chap who knows all the signals by heart and can send and receive flag messages almost as fast as you can write down the words.
The Flashlight System.—There are two methods used for sending signals at night over short distances, and both are done by means of light; named, these are (1) the colored light system, and (2) the searchlight system.
The Colored Light System.—In this system incandescent electric lights of high candle power are placed back of bull’s-eyes, or lenses, made of colored glass, and these lights can be switched on and off and so form combinations that spell out words just as the colored flags do. This system is very much used for short range signaling at night.
The Searchlight System.—A searchlight, that is an electric arc light set in front of a silvered reflector, can be seen for long distances, and so it, too, is largely used for night signaling.
The searchlight, which can be turned in any direction, has a movable shutter, or metal disk in front of it, fixed to a handle, and when this is worked up and down like a telegraph key, the shutter cuts the light off and lets it shine forth accordingly.
By working the key, and hence the shutter, the light is broken up into dots and dashes of the regular Morse telegraph alphabet, and these short and long flashes are read by the operator on the other boat.
The Wireless Telegraph System.—The wireless telegraph has all the other systems of signaling, when the submarine is afloat, beaten by miles.
Among its advantages are (1) it can be used in the daytime as well as at night; (2) the electric waves it sends out cannot be seen and this makes it harder for an enemy ship to locate the boat it is on, and (3) its signaling range is not cut off by the curvature of the earth.
The Parts of a Wireless System.—There are three chief parts to every wireless telegraph system, and these are (1) the sending apparatus, or transmitter, as it is called; (2) the receiving apparatus, or receptor, as some “high-brow” has named it; and (3) the aerial wire, which is used for both sending and receiving.
The sending apparatus is made up of (a) a source of current, which on a submarine is the storage battery; (b) an induction coil; (c) a telegraph key; (d) a tuning coil; and (e) a condenser.
The receiving apparatus is formed of (a) a tuning coil; (b) a condenser; (c) a detector; and (d) a pair of head telephone receivers. A wireless telegraph set is shown in Fig. 56, A and B.
Both the sending and the receiving apparatus can be connected with the aerial wire by means of what is called a throw-over switch, the purpose of which is to connect the aerial to the transmitter when messages are to be sent out and to connect the aerial to the receiver when messages are to be received. Thus only one aerial is needed.
How Wireless Works[28]—When a wireless message is sent the operator makes and breaks up the current from the storage battery into dots and dashes by means of the telegraph key.
This interrupted low pressure current flows through the induction coil and this changes it into a high pressure current which makes a jump spark. The spark in turn changes the high pressure current into high frequency currents, or electric oscillations, as they are called; and as these run forth and back over the aerial wire they set up waves in the ether which are called electric waves.
These electric waves are exactly like light waves, but they are so long that the eye cannot see them. The tuning coil and the condenser are used to give the waves whatever length the government says they must have.
When the electric waves that are sent out by the aerial of the transmitting station strike the aerial which is connected with the receiving apparatus of another ship and the operator is listening in, the waves are changed back again into high frequency currents, and these run to and fro on the aerial wire and up and down through the tuning coil, the condenser and the detector.
The latter instrument changes the high frequency currents, which are alternating, into an interrupted direct current; and these in turn energize the telephone receiver, with the result that the dots and dashes sent out by the sending operator are reproduced by the telephone receiver, when they are heard by the receiving operator who is listening in.
The tuning coil and condenser enable the operator to tune his receiving apparatus to the length of wave which the transmitting station is sending out, and this operation is called tuning in.
The wireless station of a submarine is usually located in the navigation compartment. Although the aerial is neither high nor long, messages can be sent to upwards of two hundred miles and received over much greater distances.
Wireless allows the submarine not only to keep in touch with its base but also to pick up and intercept messages from enemy ships, and though the operator may not be able to decipher them it is possible for him to determine in about what direction and at about what distance the ship is.
Another use to which wireless is put is signaling between submarines that are doing patrol duty at the same time but which are too far away from each other to use either flags or lights.
Wireless telegraphy cannot, however, be used when the submarine is under water, for water absorbs the electric waves in exactly the same way that it absorbs light waves. But taken all in all, wireless is by far the most important of all the signaling systems yet invented, and it is the only one by which messages can be sent and received by either day or night, over long distances and in any kind of weather.
Underwater Signaling Systems.—As I have said before, there are two kinds of signaling systems used by a submarine when it is under water.
While both systems leave much to be desired—for neither can begin to come up to wireless, either in ease of operation or in signaling range—as they are the only known means by which underwater communication is possible, there is nothing to do but to use them.
The Bell or Violin System.—This is a signaling system that is widely used on ocean going vessels of all kinds to send out warning signals in thick weather.
It is a system in which a large bell or other vibrating apparatus sets up sound waves which travel in every direction through the water; when these waves reach another craft they are heard by means of a telephone receiving apparatus.
Now, water will carry sound about ten times as far and four times as fast as air; that is to say, if a bell is struck a blow in air and the sound waves it sends forth can be heard a distance of half a mile, then the same bell if it is struck when it is submerged in water will send out waves to a distance of five miles.
The sending apparatus consists of either a bell (see Fig. 57), the striking mechanism of which is worked by electricity, or of a large saw-toothed wheel which revolves rapidly against a tight wire and in consequence sets up a musical note. This latter kind is called a violin transmitter.
Whichever is used is lowered through a hatch in the hull of the submarine, and the bell is rung or the wheel is rotated by an electro-mechanism, which sends out sound waves to distances of from 5 to 15 miles.
The receiving apparatus (shown in Fig. 57) is formed of an ordinary telephone transmitter, and this is fixed in a small iron tank filled with water and bolted to the inside of the skin of the hull. There is one of these transmitters on each side of the ship, and each one is connected with a battery and a pair of head telephone receivers placed in the navigating compartment.
When the bell or violin of another submarine, or the base ship, sends out its message in the Morse alphabet the sound waves, as you will see by looking at Fig. 58, travel through the water and strike the hull of the ship, go through its skin, set the water to vibrating in the tank, and this, acting on the telephone transmitter, makes it vary the electric current of the battery; the varying current flowing through the telephone receivers reproduces the distant sound of the bell or the violin wheel, and the operator on the submarine hears it.
The receiving apparatus also serves to detect the presence of an enemy ship when it comes within torpedoing range by the sound waves set up by and by which are sent out through the water by the rapid turning of the ship’s propellers.
The Electric Current, or Conductivity, System.—In this submarine telegraph system the water, which is a fairly good conductor of electricity, is made to carry an ordinary battery current between the sending and the receiving stations.
Since the water conducts the current of electricity, it is easy to see why it is called a conductivity system. It is also called an underwater wireless system, but while it is wireless in the sense that there are no connecting wires between the two stations, you must not confuse it with the real wireless system, which uses electric waves, for in the former the energy decreases as the cube of the distance and in the latter only as the square of the distance.
The Parts of the Conductivity System.—There are three principal parts to this system, and these are (1) the sending apparatus; (2) the receiving apparatus, and (3) the submerged copper plates which conduct the current from the sender into the water and from the water into the receptor.
The sending apparatus consists of (a) a source of direct current, and the storage battery supplies this; (b) a reactance, or kick coil, as it is commonly called; (c) a rotating interruptor, and (d) an ordinary telegraph key.
The receiving apparatus is made up of (a) a telephone induction coil, and (b) a pair of head telephone receivers. All of this is shown in Fig. 59.
One of the submerged copper plates is fixed to the bow of the submarine’s hull, and the other is secured to the stern, in order to get the plates as far apart as possible. These plates are connected to a throw-over switch, so that either the sender or the receptor can be connected to the plates as the operator wishes.
How the System Works.—The instruments of the sending apparatus are connected up as shown in Fig. 59. Now when a message is to be sent from one submarine to another, the operator sets the rotary interruptor, which is run by an electric motor, to spinning, and this makes and breaks the current several hundred times a minute as long as he holds the key down which closes the circuit.
The result is that each dot and dash he makes is formed of a large number of separate currents, and as these flow through the reactance coil, it gives each one a little kick and sends it out into the water through the copper plates; the currents then spread out between and from the plates in closed lines which extend to very considerable distances, as shown in Fig. 59.
When these electric currents reach the plates of the receiving apparatus on the submarine where the operator is listening in, they flow up the wires and through the primary winding of the telephone induction coil; these broken up direct currents flowing through the primary coil set up alternating currents in the secondary coil and also raise the low pressure currents into high pressure currents—that is, currents of a higher voltage, as it is called.
These alternating high pressure currents then flow through the telephone receiver, and by varying the strength of the magnet of the latter the dots and dashes of the sending station are reproduced and the receiving operator hears them as a musical buzz.