222 



BELL SYSTEM TECHNICAL JOURNAL 



The expression for 7" or T — To will have a maximum at co = wo 

 if b is large enough. The value of the maximum may be increased 

 by increasing b and its location on the frequency scale may be changed 

 by varying coq. A family of curves of /o(r — To) for different values 

 of the parameter b are shown in Fig. 22 with the abscissa ///o. 



To illustrate the combination of the resonant lattice type with 

 the simple lattice type, add one section of the former with b = 2, 

 fo = 2,190, to the seven sections of the latter already applied to the 



0.027 

 0.026 

 0.025 

 0.024 

 0.023 



(0 

 O 



z 

 o 



O 0.022 



Hi 



'^ 0.021 

 ? 0.020 



liJ 0.019 



P 0.018 



0.017 



0.016 



0.015 



8 SECTIONS 6 SECTIONS 



'"21 



{SECTION 



L,=0.5h L2=0.25h L3=0.42h L4=.059h 



C|=0.2mf q2=0.lmf C3=0024mf C4 = 0.l7m f 



SOLID CURVES OBTAINED FROM COMPUTATIONS FOR 



154 MILES OF H-I74-SIDE CIRCUIT. 

 DOTTED CURVES OBTAINED FROM OSCILLOGRAMS 



FOR 154 MILES OF H-I74-SIDE CIRCUIT. 

 CURVES As. C=TIME OF RISING TO HALF 



VALUE WITHOUT COMPENSATOR. 

 CURVES B&D=TIME OF RISING TO 



HALF VALUE WITH COM 

 — r---_ PENSATOR 



400 



600 



800 1000 1200 1400 1600 1800 



FREQUENCY IN CYCLES PER SECOND 



2000 2400 



Fig. 23 — Transients in loaded lines with and without phase compensator 



cable (Fig. 20). The dotted curve for T — To, which results, is 

 practically zero over most of the frequency range. The value of /o 

 was determined so that the delay curve for the resonant lattice type 

 would be complementary to the curve for the remainder of the circuit. 



The combination of the two types of lattice network is effective in 

 correcting even the large amount of phase distortion which results in 

 transmission over the medium heavy loaded cable. Fig. 23 (which 

 is reproduced by courtesy of Mr. H. Nyquist) shows a design for use 

 on 154 miles of H-174 side circuit. The experimental results, obtained 

 from oscillograms, are seen to be in close accord with the computed 

 results. 



The improvement due to correction of phase distortion by means 

 of the phase compensator circuits employed for picture transmission 

 is illustrated in Figs. 24o, 246 and 24c. Fig. 246 is from a negative 

 which was transmitted over a 352-mile H-174 circuit without phase 



