VISUAL SYSTEMS OF TRANSIENT COMMUNICATION 



263 



practicable, would become an extremely use- 

 ful method for transient communication. 



The Sound Spectrograph 



The Bell Telephone Laboratories and 

 other research units have been developing 

 (1, 9) over the past few years the sound 

 spectrograph, a device which picks up sound 

 waves, converts them into electrical energy 

 patterns (which may be transmitted over 

 distances by various means, although this 

 has not yet been done), and renders the dis- 

 tribution of energy over the audible spec- 

 trum visible as a complex pattern of illumi- 

 nated areas on a moving phosphor-coated 

 belt. Theoretically, this system renders 

 speech "visible," and, in a sense, it does. 

 However, the "visible speech" which is so 

 ingeniously produced is not easily intelligible 

 speech. Research on visible speech indi- 

 cates that eventually people may be trained 

 to understand perfectly (i.e., to respond ap- 

 propriately to) the visual patterns produced 

 by speech, so that auditory communication 

 can be converted with complete faithfulness 

 into visual communication. However, it is 

 already apparent that such training requires 

 not days, but months. Because of the great 

 time required to learn to discriminate the 

 stimuli presented, and because of the bulk 

 (and probable unreliability) of the equip- 

 ment involved, sound spectrographs are not 

 likely to play any role in military communi- 

 cation in the foreseeable future. Visible 

 speech may prove a useful research tool in 

 phonetics, in speech pathology, and perhaps 

 with further developments, it may become a 

 practical aid to the deaf. 



Radio Teletype 



This will doubtless prove one of the most 

 effective and rapid methods of handling ex- 

 terior communications, both persistent and 

 transient. With proper coding methods, it 

 seems to meet the criteria of a good commu- 

 nication system, whether visual or auditory. 

 It does not, on the other hand, lend itself 

 readily to the solution of the problem of in- 

 terior communication, or to communication 



with vessels or stations lacking special 

 equipment. 



Infra-Red Signalling Systems 



In the recent war, methods of blinker sig- 

 nalling employing infra-red radiation were 

 devised (8). The receiver was enabled to 

 respond to such blinker by use of a special 

 viewing instrument that converted the 

 modulated infra-red radiation into visible 

 light through the use of electronic optics and 

 a phosphor screen. Such a system is essen- 

 tially a refinement of ordinary visual blinker, 

 and is subject to the same criticisms as those 

 made in the section on such communication, 

 except those relating to security. 



Infra-red reflecting paint, with appropri- 

 ate viewing devices, has been proposed as a 

 means which might be employed in solving 

 the problem of recognition. However, the 

 difficulties of altering daily the pattern of 

 infra-red reflecting paint on the vessel to be 

 identified, and of persuading an excited pilot 

 to look at his contact through a pair of easily 

 misplaced goggles, make this a not very 

 fruitful suggestion. 



Telautographs 



The telautograph seems useful in railroad 

 stations, where a bulky mechanical-electric 

 system of reproducing handwriting is under 

 no great stress. In the military situation, 

 the mechanical, spatial, and temporal de- 

 mands make the reproduction of handwriting 

 at a distance of limited usefulness. 



Radar 



In the recent war, a surprising amount of 

 visual communication was effected by use of 

 the interference patterns which can be set 

 up on the radar scope. Many vessels, by 

 keying their radar signals according to the 

 conventional blinker and radio codes, were 

 able to set up temporal patterns of interfer- 

 ence that could be read like blinker code on 

 the scopes of other vessels employing the 

 same types of radar. Showing many of the 

 limitations of these methods, radar interfer- 

 ence communication (in its present state) 



