PROPERTIES DESIRABLE IN TRANSIENT COMMUNICATION SYSTEMS 



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produced in the visual or auditory field of the 

 receiver by the sender, and to which the 

 receiver responds. 



Persistent communications have tended to 

 be largely visual, owing to the multiplicity of 

 such symbols which are available in our 

 culture, and to the relative ease with which 

 they may be recorded and reproduced. 

 Transient communication, on the other 

 hand, tends to be auditory, and more spe- 

 cifically, usually employs the voice, since it 

 requires both speed and well-established hab- 

 its of response to symbols. Speech meets 

 these requirements well. It is the area of 

 transient communications in which we shall 

 examine the possible role of visual methods, 

 since their utility there has been but super- 

 ficially investigated. 



A final type of distinction which it will be 

 convenient to make is that between exterior 

 communications and interior communications. 

 The former refers to couples between persons 

 on a vessel with persons off of it, and the 

 latter refers to communication among per- 

 sons all of whom are on one vessel, but who 

 may be in different compartments. 



Just so long as information transmitted by 

 one person to another is not invariably re- 

 ceived correctly, and at the appropriate time, 

 and acted upon appropriately, there exists a 

 need for continued research on communica- 

 tion. Since developments to date have by 

 no means eliminated a variety of difficulties 

 in communications, it would appear that a 

 field for research remains. 



Properties Desirable in Transient 

 Communication Systems 



Before discussion of the several visual sys- 

 tems which have been employed for tran- 

 sient communication, it is advisable to sur- 

 vey briefly the considerations which must 

 be taken into account in designing and evalu- 

 ating such systems. 



Speed 



A communication system carrying tran- 

 sient messages must transmit them without 



delay to the receiver, and must stimulate the 

 receiver in such a way that he, in turn, does 

 not delay in responding. Systems, then, 

 which require a time-consuming procedure 

 of transmission, such as semaphore or man- 

 ual radio code, or of reception, such as 

 blinker, are inferior to such systems as radio 

 teletype, telephone, and the engine-order 

 telegraph. 



Precision 



A communication system should be spe- 

 cifically designed to carry stated information 

 in a precise and unequivocal way. It should 

 permit no misunderstanding of the message. 

 Signs employed should be unequivocal; as 

 stimuli they should be easily discriminable. 

 The diving alarm is an example of such a 

 precise and unequivocal auditory communi- 

 cation system, as are the engine-order tele- 

 graph and the sound-powered telephone 

 when used in the absence of background 

 noise by well-trained personnel. 



Identification and Acknowledgment 



The system should provide for the clear 

 identification of the sender, and of the in- 

 tended receiver. It should further provide 

 for a clearcut acknowledgment of the mes- 

 sage, which is preferably a repetition of the 

 message in the reverse direction, since this 

 procedure ensures that misunderstandings 

 are immediately revealed. 



Simplicity 



Simplicity is a merit in communication 

 systems. This simplicity should lie not only 

 in the design and construction of the instru- 

 ments employed, but also in the method of 

 use. It should be possible for persons of in- 

 ferior intelligence and training to use them 

 properly. 



Attensity 



The system should demand the attention 

 of the receiver. Since transient communica- 

 tions are almost always aperiodic, the sender 

 must be able to prepare or set the receiver 



