How the Wireless Telephone is Supplementing the Wire System in the Broad Field of Voice Communication
IT has been the policy of the Bell System to build a telephone plant which would give universal service of the highest possible quality. In building up the nation-wide plant required to give service to the people in all parts of the United States, the solution of the technical problems arising in the business has at all times been undertaken in accordance with the thorough methods of scientific research.
The scientific laboratories of the Bell System, which sprang from a tiny workroom with but two workers, have grown until they employ 2,800 persons. In these laboratories--the largest industrial laboratories ever devoted to the application of science to human affairs--not only has no effort been spared to develop wire transmission, but also the most careful examination has been made of every other recognized means of transmitting the human voice, especially the radio or wireless telephone. By the development of many different radio methods and systems, and the design and construction of different types of radio equipment during the past decade, the staff of the Bell laboratories has made numerous and very fundamental additions to the knowledge of this method of communication.
In this connection it may be pointed out that the first transmission of speech by means of electromagnetic waves was accomplished by Alexander Graham Bell, in 1880, with his so-called radiophone. Instead the long wave lengths with which wireless messages are to-day transmitted, this device made use of the very short waves of the visible spectrum, a beam of light being varied in intensity in accordance with the variations of the speech waves.
Turning to a consideration of the modern developments of the radio art, it will be recalled that the engineers of the Bell System transmitted speech by wireless telephone from Arlington, Va. to Paris and Honolulu in the autumn of 1915, thereby establishing the historic record for American engineers of being first to transmit the voice across the Atlantic Ocean. Furthermore, in transmitting the voice to Honolulu a long-distance record was achieved which has not yet been equaled by others.
The Bell engineers had a notable part in solving the many radio problems which arose during the recent war, and designed many types of radio equipment for the American forces both for communicating with ships and with airplanes.
Where Wireless Telephones Are Working
No commercial uses have yet been made of the Company's trans-oceanic telephone development because of the many practical difficulties which are involved in the application of radio, chief among which are the disturbances due to "static" and other interferences.
More recently, the first two wireless telephone stations available for public use have been erected on the California coast. These stations supply every-day telephone service between the Island of Santa Catalina and the mainland, and are an integral part of the Bell System so that a subscriber on the Island can call any number in Los Angeles, or in fact, any number throughout the entire Bell System. A submarine cable would give better and more economical service to the Island than the radio telephone, but manufacturing conditions growing out of the war were such that this cable could not have been obtained within the time desired. In view of this fact, together with the fact that the installation of a wireless system would provide valuable experience regarding the use of the radio telephone in rendering commercial service, the decision was made in favor of the radio system.
The Company has also performed extensive investigations into the matter of ship-to-shore telephony. For a year past, an experimental equipment has been maintained by the Bell engineers on the steamships Gloucester and Ontario in conjunction with their radio stations on the Massachusetts coast and on the New Jersey coast. Utilizing these experimental stations, they have conducted practical scientific investigations into the best methods of maintaining communication between ships at sea and the wire plant of the Bell System throughout the United States.
The progress made in this work is well illustrated by a demonstration given lately in honor of the delegates to the International Communications Conference, during which conversation was exchanged between Catalina in the Pacific Ocean and the S. S. Gloucester in the Atlantic. Speech was transmitted by radio telephone from the Gloucester through the New Jersey station, and thence by wire across the continent to Los Angeles, and thence by radio telephone to Catalina. More recently, apparatus has been developed whereby a single land station can maintain a different two-way conversation with each of three ships at the same time.
Still another achievement fresh in the mind is the joining of the overland wire circuit from Key West to Los Angeles with the new submarine telephone cable to Cuba and with the radio telephone to Catalina, to the end that speech was transmitted between an island in the Atlantic and an island in the Pacific.
The extensive experience of the Bell engineers in trans-oceanic and ship-to-shore radio telephony and in supplying commercial radio telephone service on the Pacific coast, has provided trustworthy data whereby they can judge concerning the practicability of radio in the various fields in which it might be applied. Their studies show that the characteristics of wireless transmission are such as to make it particularly useful as a means of supplementing the wire systems in those instances where, from the nature of the case, it is impossible or impractical to employ wires.
Thus the broadcasting of information of general interest over land and water is a service which cannot be rendered by wires and for which radio with its messages carried in all directions at the same time is well suited. The broadcast distribution of time signals and weather and market reports to mariners, farmers, and the like, and the simultaneous dissemination over a wide area of important items of news is likely, as time goes on, to become one of the most important uses of radio communication in which both the radio telegraph and telephone will play their respective parts. For those purposes, the fact that the messages can be picked up by all who have proper receiving stations, is clearly a decided advantage.
On the contrary, however, when radio messages are intended only for certain stations, the fact that they spread out in all directions, causing lack of secrecy, is a defect. For the distribution of press dispatches intended only for particular stations, radio could not be employed unless some method of preventing the reading of messages at unauthorized stations is obtained.
In the transmission of news, speed is an essential factor, and while it is not impossible at the present time to put news dispatches in cipher by ordinary methods, the time required for enciphering and deciphering makes these methods objectionable. Accordingly, the Bell research laboratories have worked on the problem of applying to radio telegraphy the quick cipher or secret method of wire telegraphy which their engineers developed and which was used with marked success upon wires by the Signal Corps during the war. It is a secret means of telegraph communication, and while the ciphered message may be heard at all radio stations, it can be interpreted only by those who have the cipher apparatus and key. This instantaneously enciphers the message at the sending end and deciphers it at the receiving end, where it appears immediately in printed page form ready for use. The work done upon this system of secret telegraphy by the engineers of the Bell System promises to be generally available and for the benefit of radio telegraphy.
The Bell engineers have also attacked the problem of privacy in radio telephony and have given an experimental demonstration of a method which they have devised, whereby ordinary receiving stations can hear nothing but unintelligible sounds; yet at all stations equipped with the necessary apparatus and in possession of the requisite operating information, the spoken words can be understood.
Before the advent of radio, there was no very effective means of communicating with ships and other moving stations, and it is by virtue of the inherent characteristic of all radio messages--that they spread out in all directions--that the wireless telegraph has greatly increased the safety of travel at sea, becoming a blessing to the mariner and to those who entrust themselves to his care.
In the future, it is expected that the wireless telephone will also play an important part in this field in which the wireless telegraph is now of inestimable value. As noted above, the developments necessary to this end have been carried well toward completion by the Bell engineers, and when certain problems, largely commercial in their nature which are peculiar to ship-to-shore telephony, are disposed of, the wireless telephone will serve to put ships in communication with the telephone lines on land to the same extent that the Island of Catalina is now connected to these lines.
In addition to its uses in navigation, the wireless telegraph has taken its place beside the submarine cable as a means of trans-oceanic communication. In this field, the wireless telephone is expected to play its part, for while it is possible to signal by telegraph through the trans-oceanic submarine cables, it is not possible to talk through them.
The wireless telegraph finds its best field across large bodies of water such as the Atlantic and Pacific Oceans where the only wire communication possible is by means of submarine cables. Across the oceans the relative advantages of the cable and the radio are difficult to appraise. Each has advantages over the other, and each has its disadvantages, and each is successfully carrying its share of the international telegraph traffic of the world.
While the radio telegraph does not function as successfully over large areas of land as over corresponding areas of water, the telegraph wire cable over land is vastly more efficient than is the submarine cable of an equal length. The submarine cable consists of one conductor, whereas the land cable, although less than three inches in diameter, may carry as many as 600 conductors. Such a cable, when constructed and operated in accordance with the latest scientific discoveries, can be made to carry over 5,000 telegraph messages at one time, as compared with only two messages carried at one time by the submarine cable.
While the number of land cables may be increased without limit and can carry traffic far in excess of that which ever will be required, the number of messages which radio can carry at one time is distinctly limited due to the fact that each radio message tends to spread out in all directions, thus traveling through the same region in which many other messages are traveling. As has been aptly said, the ether is a universal party line constituting a single conductor which must be used in common by all the world.
Although ingenious methods have been devised whereby the number of simultaneous radio messages may be largely increased, the ether can at best carry only a small portion of the total world traffic. The best field of radio is for long distance trans-oceanic communication, for broadcasting, for the radio compass and for auxiliary radio fog signals given out by lighthouses, for innumerable military and naval purposes, and for transmitting messages to and from moving stations and between places where wires are not available. When all of these necessary services are fully provided for, the capacity of the ether for conveying messages simultaneously without interference will be taxed to the limit.
Thus the characteristics of radio messages, causing them to spread out over large areas and enabling radio to be of inestimable service in certain fields, stand in the way of its extensive use on land where it is possible to provide wires which are nothing more or less than pathways for guiding or directing the electric waves in the ether between any desired points, however numerous they may be or wherever they may be situated. By means of these wire guides, millions upon millions of messages may be carried simultaneously without interference with each other.
It has often been said that, had the course of scientific development been reversed so that radio transmission preceded transmission by wire, the discovery that wires can be used to guide the ether waves would be considered one of the marvels of science. By their use, the otherwise uncontrolled ether waves are caused to follow any predetermined pathways, flashing thousands of messages to and fro under our city streets without the slightest interference, each message following its allotted course, whether up through the intricate structure of a thirty-story office building, or to the far side of the continent, there to be received by him--and him alone--for whom it is intended.
The natural characteristics of radio and wire transmission are, therefore, fundamentally different. Each is performing a service for which the other is unsuited and each is supplementing the other to the end that all important needs for communication are being provided for as rapidly as they arise. For the large amounts of traffic on land, which must be handled with certainty and a minimum of cost, the use of wires is necessary. But as an agency for communicating over wide stretches of water, with moving conveyances generally, for a host of maritime and military purposes, and for the broadcasting of information, radio to-day is rendering services of the greatest value, and all considerations point to the conclusion that in these fields its use will become of ever greater importance.