THE MARCONI LABYRINTH.

Otago Witness, Issue 2949, 21 September 1910, Page 79

THE MARCONI LABYRINTH.

Wire-ess telegraphy is but 15 years old,, yet it has become a vital aid to the safety of shipping, and an instrument of everincreasing value to commercial and social life. It has recently shown great possibilities in the tracking of criminals, it has provided a new 1 factor in offensive and defensive warfare, and it has opened up the prospect that communication between nations will become much more cheap and easy than at present. No familiarity with the subject, however, ca.r quite remove the vaguo feeling of wonder with which one sees the operator draw his message out of space, and decipher the message conveyed to him from another station, maybe a thousand or more miles away. ' —An Electric Eye.—

Yet, essentially, there is nothing more wonderful in wireless telegraphy than in the response of the eye to sunlight. Our eyes are sensitive to the light vibrations set up by the sun millions of miles away. A wireless telegraphic, transmitter sends similar vibrations through the ether, and these vibrations are recorded on an in etrument designed to be sensitive to them. For this reason Lord Kelvin has described a wireless telegraphic receiver as an "electric eye"—a very accurate simile. In its bare outlines Marconi's system of telegraphy consists in setting in motion, by means of a transmitter, ceitain electric waves, which, passing through the ether, are received on a distant wire suspended from a mast, and registered on the receiving apparatus. Throw a stone into a quiet pond and watch the waves which are instantly formed and spread out in every direction ; the water does not move, except up and down, yet the wave passes onward indefinitely. The System.—

Thie is the principle that Marconi has employed in developing wireless telegraphy. Electricians had already discovered how to incite electric waves, also, to a certain extent, how to control them. Marconi improved upon their methods, and devised a clever instrument to register the presence of these waves. This instrument, which was known as the coherer, was the very crux of the system, without which there could have been no wireless telegraphy. The coherer is a small glass tube, about 2in long and as thick as a lead pencil. It is plugged at each end with silver, and filled with finelypowdered fragments of nickel and silver. The waves from the transmitter, when received by th« coherer, draw the particles of nickel and silver together: they immediately become a good conductor of electricity, and a current from a battery near at hand operates the Morse instrument, and print out the message from the transnutter in dot and dash. The mechanism, however, has in turn been improved, the instrument now used being known as the magnetic detector. Thie apparatus is composed of a small box containing a simple clockwork appaiatus, operated on two small ebonite pulleys. The message, when received at the mast, passes to this apparatus, and thence to an cidinary telephonic receiver over the operator's head. What the operator hears is really a reproduction of the sparking of the transmitter at the other end, and from this series of dashes he reads his message. The Key to the Labyiinth

Following the analogy of the stone castin the pond, with the ripples circling onward, it is obvious that any sent, say, from England to America would be heard by anyone with a corresponding receiver, say, in Iceland, Russia, or Africa'' This was the great problem with which the inventor had to contend: how to convev a message to any given receiver witho •everyone within radius being übls to rev., the message as well. Without secrecy no system of wireless telegraphy could ever attain any degree of importance, or even hold its own against the older cable communication. To do this Marconi adopted, for long-distance work, a system of tuning—that is to sav, he so constructed a receive'.- that it would only respond to a transmitter radiating exactly the same number of vibrations per second. The importance of this system can scarcely be over-estimated. All the ships of a fleet can be provided with instruments tuned alike, so that they may communicate freely with one another without fear of the enemy reading their messages—an impossible feat unless the secret of the tunes were known. This is the great secret of the Marconi labyrinth, the marvellous working of which has so astonished the general public the last few days.

How a Message is Sent.—

At headquarters the tune of the instrument on board each vessel is known. Thus we will suppose that the Marconi Company desire to oomunicate with a certain vessel. At their office they have the tune of the instrument fitted on the vessel and the code signal or " call." They tune their own instrument to a corresponding number of vibrations—say 800,000 per second—and over the ocea.li in ever-widening circles travels the call for the steamer. " brripp brripp brippJ>rrr. Errr-brinD-brino!" So talks tiie

| transmitter as the operator works a black- ! handled key, and with each movement j of the key bluish sparks jump an inch , between two brass knobs of the induction coil. For one dot a single spark jumps, j for one dash there comes a stream of j sparks. Each spark indicates a certain ! oscillating impulse from the electrical bat- ; tery actuating the coil, and each impulse travels through space at the speed of light, or seven times round the earth -in one . second. That is all there is in the sendI ing of a Marconi message. Now, let lis 'j imagine ourselves in the little cabin of the operator on board ship. From the mast a wire runs down to his cabin, and, passing through the magnetic detector mentioned earlier in this article, terminates at a telephonic receiver attached to his head. Suddenly he hears a faint yet clear cracking sound: a long crack, a short one, and so on in regular sequence. It is the code rail to the operator from head- ■ quarters, conveying who knows what im- ! portant message? Recently another advance has been made in the science of wireless telegraphy by the introduction of the "directional aerial." This is a particular arrangement of the aerial wires, by mean 6 of which the electric waves are concentrated mainly along any definite path. Tne advantages .of this arrangement are three-fold : there is a distinct improvement in the clearness of the transmitted sound, there is a smaller expenditure of power, and the area of possible disturbances with or by other wireless stations is more limited in area. The system has one drawback, however: the necessity of knowing with a fair degree of accuracy the position of the station with which it is desired to communicate. This result is achieved by a special set of charts showing the exact position at i an time of every vessel carrying a Mari coni wireless telegraphic apparatus. Marconi's Web.— There have been many instances of the value of this science in saving life and ' property at sea. The C.Q.D. signal is a • widely-recognised signal for assistance, and has been the means of bringing help to many a distressed vessel from a hundred or more miles away, and as time goes on more and more ships of the mercantile marine will be equipped with wireless telegraphy, until such installations become recognised as necessary to the safety nnd up-to-date working of a vessel. In the British navy every battle- , ship, cruiser, and destroyer is fitted with Marconi apparatus—indeed, without this means of communication it would be scarcely possible to carry out the rapid and carefully planned evolutions characteristic of modern warfare. in military operations also wireless telegraphy is being more largely used, a portable apparatus having been designed specially for that purpose. Commercial trans Atlantic com munication is bound to develop rapidly in usefulness. Telegrams are accepted for transmission by wireless at the rate of per word to Montreal, Toronto, and New York City. To all other places in Canada and North America the Marconi Company maintain their rates 4£d per word less than those shown in the current Post Office Guide! There are two rates for lhe transmission of telegrams toships at sea. To ships within reach of the lower-power stations the rate is per word, to those only within reach of ■ the high-power station the rate in 3s per word. Future developments will lead to reduced charges, and as man's command over hitherto unknown forces of Nature increases,, it is probable that the use of wire for the transmission of messages will cease entirely, and the deep tea cable ba come a thing of the past, and the' sub urban road will no longer be disfigured with telegraph poles and wires.—H. O. B ! in T.P.'a Week!v. • '