488 BELL SYSTEM TECHNICAL JOURNAL 



sufficient to cover the weather range ordinarily experienced. The 

 increase, ii + iv, in the transfer exponent due to a change of one step, 

 such as from dry to semi-wet, was taken as one half the difference of 

 these exponents computed for dry and average-wet weather conditions 

 under which the circuit constants were known. Thus 



M 4- W = \[{a + i6)av.-wet " (« + ^'&)dry]. (72) 



The weather change network which corrected this consists of two 

 parts shown in Fig. 17, an attenuation equalizer and a phase corrector, 

 the latter being required primarily because of the phase constant 

 necessarily introduced by the former. 



This attenuation equalizer has the same form as the low-frequency 

 network for dry weather and was designed similarly from the data 

 (according to (8)) 



/i = 0, Ai = .466 napier; 



/2 = 20,000-^, A2 = .150 napier. 



The assumption for the network of .150 napier at 20,000 cycles per 

 second was found to result in a satisfactory attenuation characteristic 

 over the entire frequency range. Then 



Po =29,872-10^; Q^ =11,763-10^; 



flo = .22887; hi = .71099- 10"^ 



i?ii = 274.62 ohms; Go = .04120 mf. 



Transforming to the bridged-T (la) structure, c = l/oo = 4.369 and 

 the elements of Fig. 17 become 



Ri = 68.65 ohms; R2 = 1242 ohms; 

 Cz = .08240 mf.; U = 14.83 mh. 



The phase corrector was Network 13, Appendix IV, designed in a 

 manner somewhat different from that usually employed. If D again 

 represents the phase departure of the uncorrected phase from linearity 

 to the value at 20,000 cycles per second, it was found that 



at/i = 10,000^, Di = - .111 radian; 



at/2 = 20,000 ~, D2 = 0. 



To give a satisfactory resultant phase which is linear through /i and /o 

 irrespective of its slope, the phase corrector only needed to have a 

 phase constant, Bi at/i and B2 at/2, such that 



D,-^B, = \B2, (73) 



