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BELL SYSTEAI TECHNICAL JOURNAL 



the cable itself) in the proper proportions to insure the steepness of 

 building-up of the arrival curve and the maintaining of the tail of 

 the wave. Terminal corrective networks ^ in combination with 

 vacuum tubes were designed to obtain the requisite derivatives. 

 Such a terminal corrective network is shown in Fig. 4, where the 



SENT 



1000 CYCLES 



SENT 



1500 CYCLES 



RECEIVED 



mm 



SENT 800 & 1600 CYCLES 



RECEIVED 



il^lHtltlmHimmmm 



Fig. 3 — Transient distortion in a 600 mile length of H-174 loaded cable 



resistance Ri is a distortionless one-way thermionic tube and V(ci)) 



the output voltage. Examination of this network in the light of the 



more recent study of phase distortion correction from the steady state 



point of view has shown that it does also correct the phase distortion 



of the cable and provide some attenuation equalization as well. 



Although the design of corrective networks on the basis of the 



steady state phase has usually been found more simple than on the 



transient basis, a knowledge of the arrival current or voltage as an 



® See references 5 and 6. Also, for the development of distortion corrective 

 circuits with vacuum tube amplifiers, or "signal shaping vacuum tube amplifiers" 

 as they are called, in connection with their application to the new permalloy cables 

 of the North Atlantic, see references 7 and 8. 



