TRANSATLANTIC RADIO TELEPHONY 367 



been derived for positive values greater than x but negative values 



greater than — x are equally probable and therefore the fraction of 



the time that the absolute value of voltage is equal to or greater than 



X is 2PxN or 



P\xiN = 2P,n. (404) 



Specific cases which approximate the existing conditions of long- 

 wave transatlantic reception have been calculated from equation (404) 

 and are shown in Fig. 21. These curves are based on the following 

 assumptions: 



1. That the number of stations lying in the restricted frequency 

 range is A^ = 100 and N = 25. 



2. That each station contributes unit peak voltage to the input of 

 the radio receiver. 



3. That each station has its key depressed 15 per cent of the total 

 time during any day. K = 0.15. 



4. That transmissions from all stations are random. 

 Considerable valuable assistance in the preparation of this appendix 



has been obtained from Dr. F. H. Murray of this department and 

 the authors wish to express their appreciation of this aid. 



