262 



VISUAL COMMUNICATION 



when a submarine is submerged. (5) Rec- 

 ognition color-patterns can be changed daily. 

 Release of dyes by a submarine might be 

 brought about in any of several ways. Four 

 small guns, fixed to the snorkel, might fire 

 shells loaded with dyes^ of the appropriate 

 particle size, in each of four directions. 

 Fuse mechanisms could then explode the 

 shells at a height above the sea surface such 

 that particles of dye stuff are scattered 

 evenly and closely over a wide area. Thus, 

 when a friendly plane approaches, the CO., 

 firing the four guns by remote control, could 

 produce within a few seconds four large 

 colored patches of water, in a spatial pat- 

 tern determined by the date and time of day. 

 Such a pattern, viewed from shooting range, 

 offers a minimal basis for misinterpretation 

 by friendly aircraft, despite its use of color. 

 Another method might employ high-pressure 

 jets of heavily dyed water emitted squid-like 

 by the submarine. 



Pyrotechnics 



Flares and smoke bombs have been em- 

 ployed in visual communication, but because 

 of their lack of flexibility their use has been 

 confined to recognition signalling and to dis- 

 tress signalling. In certain situations they 

 probably will remain indispensable, e.g., 

 flares for emergency use at night and smoke 

 bombs for simple communication from a 

 completely submerged submarine to a sur- 

 face vessel. Flares have the disadvantage 

 of revealing the presence of a submersible to 

 enemy craft within a wide range. The situa- 

 tions in which pyrotechnics can be used are 

 so limited, and the ease with which they are 

 mistaken for unfriendly activity is so great, 

 that they cannot be considered as a useful 

 communication system except under very 

 restricted conditions. 



For exterior communication, all of the 

 methods we have discussed thus far share 



^ If the dj^es developed also had the property 

 of reflecting the radiation employed in radar, 

 they could provide a still further basis for recogni- 

 tion. 



certain disadvantages. They are dependent 

 upon visibility — the state of the atmosphere. 

 They lack flexibility, being perhaps unduly 

 limited by the codes employed. And they 

 are slow, and involve security risks, in that 

 almost all may be intercepted by anyone 

 within visual range of the sender. 



The remaining methods of mediate visual 

 cormnunication present the visual stimuli 

 proximate to the receiver's receptors. In all 

 of these methods, the visual stimulation is 

 presented by some device which has con- 

 verted into patterns of light some other form 

 of energy, such as an electrical current, elec- 

 tromagnetic radiation outside the visible 

 spectrum, or mechanical energy. These in 

 turn have been set up by the sender, either 

 by his control of radiation as in radar; by his 

 motions "visually" responded to by an elec- 

 tric system, as in television; by his move- 

 ments, as in the telautograph; or by his con- 

 trol of special electrical circuits, as in the 

 engine-order telegraph. None of these 

 methods are limited by the meteorological 

 visual range, and they are suited to commu- 

 nication between any two stations whether 

 these stations are on different ships, or ship 

 and plane, on ship and shore, or only in 

 different compartments of a single vessel. 

 The various methods will be discussed in the 

 order of their probable utility to the services, 

 rather than in the order of their complexity. 



Television 



Television systems are ideal for the trans- 

 mission of visual information of any type 

 over great distances. They enjoy both the 

 advantages and disadvantages of the spe- 

 cific systems whose symbols are transmitted, 

 with added disadvantages peculiar to tele- 

 vision itself. These disadvantages are the 

 complexity, size, and unreliability of circuits 

 used. With uniform equipment, and sup- 

 plemented by auditory communication, tele- 

 vision may become a useful method whereby 

 the receiver is stimulated both aurally and 

 visually by the sender, and is placed effec- 

 tively in direct contact with him. A tele- 

 vision system, then, if it could be made 



