THEORY OP THE HOli'LLXG TELEI'IIONE 



39 



Using the same constants as abo\'e the condition for howh"ni^ 

 becomes 



Ih 52 I 24°. = [93 + 7>G0/+j(43 + 150/)-^'n[ -2.14/2 + 2.3 + 



i.l4/]+jl.7/ 



(23) 



The sohition for vahies of K= 1 mf, K= 1/2 mf, and K= 1/5 mf 

 are given in Table I. When K= 1 mf and the supply current is direct 

 the solution which satisfies the phase equality is/= 506. This corre- 

 sponds to /i= 220 which is an impossible value. Therefore, no howling 

 will be sustained for this condition. For K= 1/2 mf the system will 

 howl for both direct and reversed supply current, the frequency 

 changing suddenly from 839 to 1119 cycles as the current is reversed 

 while the other variables change only slightly. 



Table I 



It is interesting to note the change in the howling frequency as 

 the value of K increases. When the supply current is negative, and 

 for values larger than 1 mf, the frequency of howling is always close 

 to 1000, as K goes from 1 to 1/2 the frequency increases to above 

 1100. For smaller values of K the frequency continues to slowly 

 increase until, for values smaller than 1/3, the system ceases to 

 sustain oscillations. For positive values of supply current no howling 

 will result until K becomes smaller than 2/3 where the frequency is 

 around 800. The frequency then increases reaching a howling fre- 

 quency around 1000 for K= 1/7. For smaller values of K no howling 

 will be sustained. 



