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BELL SYSTEM TECLINICAL JOURNAL 



Physically, this is realizable in the circuit of Fig. 8 consisting of a 

 resonant element L, C, where Wm = \l\LC, in parallel with a resistance 

 Ri. The final voltage is taken across the resistance R2 and the 

 resistance r represents a vacuum tube. This unilateral element 

 permits of suitable amplification and prevents reflection at the cable 

 terminals so that the network may be designed without regard to 

 any reaction upon the cable. 



Fig. 8 — Distortion corrective circuit for long telegraph cable 

 One section of the network of Fig. 8 with the values of the constants; 



r + i?2 = 5,000 ohms, 

 Rx = 51,100 ohms. 



L = 26 henrys 



C = 1.56 microfarads 



is used when / = 500 miles. The phase of this network is shown in 

 Fig. 5 also. Another equal network section may be added for each 

 additional 500 miles of cable but there is no necessity, of course, for 

 the sections to be equal. If it contains a one-way thermionic tube, 

 each section may be added without affecting what has gone before, 

 and the resultant phase angle will be simply the sum of all of the 

 phase angles of the separate parts. 



The improvement in the building-up of the indicial admittance 

 accompanying the use of the phase compensator is evident from 



