202 



AUDITORY SIGNALS 



There are two main reasons for automatic 

 transmission. The first of these reasons is 

 that automatic transmission does not require 

 the use of human operators on the input 

 side of the communication system. When- 

 ever there is a shortage of manpower, or a 

 shortage of space, it is desirable to avoid the 

 use of human operators. 



The second reason for using automatic 

 transmission of information is that faster 

 communication is possible. Whenever a 

 human operator is brought into the picture, 

 we have the inevitable delays due to his 

 relatively slow reaction time, plus the fact 

 that the human being has to comprehend a 

 situation before he can transmit information 

 about it. An excellent example of this is 

 gun control on ships. Before a man can tell 

 a gun director operator where to point to 

 pick up a target, he has to determine that 

 there is a target, then determine its position 

 in two or three coordinates, and then trans- 

 mit all that information by telephone. An 

 automatic signal generator could produce 

 the appropriate signals just as fast as a 

 human operator could place some pointer, 

 electronic or mechanical, on the target dis- 

 play. The total savings in time here could 

 easily approach ten seconds or more. 

 Attention should also be called to the possi- 

 bility of allowing dials and indicators to do 

 their own "talking." An automatic annun- 

 ciator w^as developed during the war (6, 7) 

 which proved highly successful in laboratory 

 tests, but which has not j^et been put to 

 practical use. This automatic transmitter 

 used a battery of magnetic tapes on which 

 were recorded various speech signals, such 

 as numbers or words. A relay selector made 

 it possible to convert the correct reading on 

 a dial into words or numbers selected from 

 the appropriate magnetic tapes, and this 

 signal then was transmitted automatically 

 to the listener. While this device was de- 

 veloped principally to provide automatic 

 transmission of a limited range of speech 

 signals, it could be just as easily used to 

 provide a variety of special tonal signals. 



In effect, this device makes it possible for a 

 dial to be read automatically, and for the 

 dial reading then to be transmitted without 

 a human operator ever seeing the dial or 

 talking over a telephone network. Its pos- 

 sible uses are many, and an investigation 

 of its potentialities should be undertaken 

 by the Submarine Service. 



Kinds of Information 



There are different kinds, or degrees of 

 precision, of information which we might 

 want to transmit in a given situation, and 

 the utility of a given type of auditory signal 

 depends a great deal on the kind of informa- 

 tion required. 



Yes-No Information. The simplest kind 

 of information is of the yes-no, either-or, 

 type. Did an event happen or didn't it? 

 Should an action occur, or shouldn't it? 

 For example, a gunner can be told to fire 

 a gun in a single positive order. If the gun 

 should not be fired, no signal is needed. The 

 tonal signal in this case can itself be a yes-no 

 type of signal. If no action is to occur, no 

 signal occurs. If the action is to occur, the 

 signal is heard. If no other information is 

 to be transmitted with this particular com- 

 munications system, then the kind or quality 

 of the tone is rather incidental. The only 

 real problem is whether the signal can be 

 heard, since there is no possibility of con- 

 fusing signals. Of course, if a particular 

 communications system has to provide in- 

 formation about several possible actions, 

 then we need as many easily distinguishable 

 tones as we have actions, but no more. 



Directional Information. A second level 

 of information can be called directional, or 

 qualitative. Here we need not merely audi- 

 bility of a signal, but directionality, as well. 

 For example, we might want a tonal signal 

 which indicates limits of tolerance, but which 

 also indicates the direction of deviation from 

 those tolerance levels. Is a gun pointed too 

 high or too low? Is the rate of fire too fast 

 or too slow? In the psychological sense, 

 yes-no information requires only audibility 



