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VISUAL COMMUNICATION 



the problem of coupling with which we are 

 concerned. Such control is effected by the 

 stimulation of the sensory mechanisms of the 

 second individual (the receiver) by the be- 

 havior of the first (the sender), in such a 

 way that he will respond in a predictable 

 fashion. The problem of communication is 

 the problem of the effectuation of such stim- 

 ulation, usually across a distance which is 

 not negligible. 



Terms 



In accordance with this analysis, a mes- 

 sage, or information, is that complex of sym- 

 bols produced by the behavior of the sender 

 to which the receiver is expected to respond 

 in a predictable way, according to the sig- 

 nification of the symbols. The sender trans- 

 mits the message to the receiver through some 

 communication system. In many instances, 

 it is desirable for the receiver to return an 

 acknowledgment to the sender, verifying in 

 detail the receipt of the message. This ac- 

 knowledgment is often a transmission of the 

 same message back to the sender by the 

 receiver. 



Communication systems may be consid- 

 ered as direct or mediate. Direct systems are 

 those in which the sender is in direct contact 

 with the receiver through the physical me- 

 dium of communication and transmits the 

 message by voice, by gesture, or other pre- 

 viously agreed upon code. In supplemented 

 direct systems, the sender or the receiver, or 

 both, may make use of special aids to com- 

 munication through the medium. For the 

 sender, these may include signal lights, sema- 

 phore flags, megaphones, or similar devices 

 for increasing the distance across which the 

 symbols produced may be seen. For the 

 receiver, special aids to vision or hearing 

 may be employed, such as binoculars, snoop- 

 erscopes, microphones and amplifiers, and 

 so on. 



Mediate system is a term reserved for those 

 methods of communication which do not re- 

 quire the possibility of direct stimulation of 

 the receiver by the sender, but which make 



use of more or less elaborate mechanical or 

 electronic devices for the conversion of the 

 energies controlled by the behavior of the 

 sender into other forms of energy, which 

 ultimately stimulate the receiver. Such sys- 

 tems range in complexity from the handwrit- 

 ten message to television, and include sound- 

 recording methods and radio. It is apparent 

 that both direct and mediate systems may 

 involve either the receiver's vision or hear- 

 ing, or both. 



Two general classes of messages may also 

 be distinguished. The first we may call 

 persistent. Persistent communications are 

 those which are not necessarily addressed to 

 a specific receiver, which neither require nor 

 expect immediate action of the recipient, 

 and which are not needed by the recipient 

 as a basis for urgent action. They are typi- 

 cally recorded in some manner, so that they 

 may be referred to or acted upon at a later 

 date. Such messages include statements of 

 basic procedures, general instructions, and 

 so forth. 



In contrast, transient communications are 

 those which either require immediate and 

 precise response on the part of the receiver, 

 or the contents of which are urgently needed 

 by the receiver as the basis for immediate de- 

 cisions on a course of action. Transient 

 messages include combat information, com- 

 mands, and status information. They in- 

 variably require extremely rapid transmis- 

 sion, and optimally, it appears, should be 

 equally rapidly acknowledged in detail. 

 They are seldom recorded, except for histori- 

 cal purposes. 



Two media of communication have been 

 of military importance: light and sound. 

 Light, as a medium of communication, in- 

 volves the production of signals which will 

 ultimately stimulate the visual apparatus of 

 the receiver, and sound involves the produc- 

 tion of stimuli affecting his auditory system. 

 These media define visual and auditory com- 

 munication, respectively. In connection 

 with communication, we shall employ the 

 term display, which refers to the set of signs 



