PHASE DISTORTION AND PHASE DISTORTION CORRECTION 209 



is also a constant resistance of the same value as the characteristic 

 impedance of the Hne. A number of general recurrent networks of 

 the so-called ' constant resistance ' type ^^ are known and such a 



o I WWWr 



Ri 



:R2 v(u)) 



Fig. 11 — Phase distortion corrective circuit for loaded cable. For 20 miles of 

 19 gauge H-44-25 loaded cable, r + R2 = 5000 ohms, Ri = 101,000 ohms, L = 0.460 

 henry, C = 0.0216 microfarad. 



network 1° has been applied to correct the distortion on the submarine 

 cable. The arrangement is shown in Fig. 12. It will be observed 

 that Zu and Z21 are inverse networks of impedance product R?-, that 



Fig. 12 — Constant resistance type corrective circuit for long telegraph cable. 

 m^ represents distortionless amplifier 



is, Zii22i = R^, which is, in general, the requisite relation among the 



network constants to provide a constant resistance characteristic 



impedance, R. In practical performance the networks of Figs. 8 and 



12, each having the basic arrangement Sn, are equivalent. Thus the 



^^ See reference 11. 

 14 



