Wave guides in electrical communication

An attempt is here made to survey the state of published knowledge of a branch of electrical engineering that has recently come into prominence and to present an introduction to it in general terms within a range sufficient to explain the development of what in effect is a new technique and its relation to other branches of electrical engineering. The first part of the paper describes the salient properties of electromagnetic waves in hollow metal tubes and reveals the great extent to which the theory of the subject had its origin in the researches of Lord Rayleigh and other investigators who, during the closing years of the last century, worked in Great Britain. It also indicates to how great an extent the development of the theory and its practical application are due to researches carried out during recent years mainly, in the United States. The second part of the paper gives a systematic account of the development of elementary equipment appropriate to hollow tube transmission, with analogies from acoustics, telephony, and radio engineering. The third part describes phenomena observed at the open ends of guides?flared or unflared?and exhibits the efficiency of these devices as radiators of energy into free space. The prospective field of application of guides embraces systems of communication operating over any distance, and providing telephone and television channels in numbers vastly exceeding those of any system of established type. When flared into horns, guides may serve in systems for broadcasting of music or television, for blind landing of aeroplanes, for detecting, locating and man?uvring of ships, and for other purposes for which at present radiators and receivers of conventional type are used. Although the usefulness of such systems may thereby be enhanced or extended in range, their mode of operation is well known and hence their description is beyond the scope of this paper. The full extent of the field of application of guides will ultimately be go- verned by costs and must, for the present, remain a matter of conjecture; but, judged from the course the development has taken during recent years, conjecture suggests that the field will be large and attractive.