12-7] IMPORTANT CHARACTERISTICS OF THE HUMAN OPERATOR 645 



Receiver Noise 

 O =1.98 Volts -RMS 

 D =7.92 Volts - RMS 

 A =19.8 Volts -RMS 

 O =79.2 Volts - RMS 



O Floodlight Condition 

 • Dark Condition 



10 



Fig 



20 30 40 



PEDESTAL AMPLITUDE (Volts) 



. 12-26 Detectability vs. Pedestal Amplitude. 



80 



A lack of oxygen will result in a decrease in the sensitivity of the eye. 

 Fig. 12-29 shows the change in absolute threshold as a function of dark- 

 adaptation time and oxygen tension. A higher threshold is an indication of 

 decreased sensitivity. The effect of lack of oxygen becomes more pro- 

 nounced as the eye becomes more sensitive. This fact is indicated by the 

 increased separation of the curves as length of time in the dark is increased. 



Man-Machine Interrelationships. The foregoing analysis has been 

 primarily concerned with the physical, physiological, and anatomical 

 aspects of the visual system. However, when the human operator is part 

 of the system, his psychological characteristics can influence system design. 

 Unfortunately the necessary data to develop a cohesive system of design 

 specifications relating to human psychological characteristics are not 

 available at this time. Therefore it is necessary to study each problem 

 and gather data that are specific to the particular problem, thus adding to 

 the general body of knowledge which will eventually lead to a systematic 

 procedure of specification. The following paragraphs will present indica- 

 tions of the kind of effort that is required to obtain data that can be used 

 in development of an airborne radar system. 



