1068 THK BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



In practice the amount of attenuation (ori) which can be canceled by 

 the repeater depends on the uniformity, the loss and the type of line. 

 The permissible magnitude is computed by conventional methods which 

 are beyond the scope of this paper. 



Fig. 8 has shown how the combination of a series and a shunt repeater 

 can annul a large part of the attenuation of a telephone line. Much may 

 be accomplished also by a series negative impedance alone as illustrated 

 in Fig. 9. In Fig. 9(a) a transmission line is again represented by two 

 networks A and B. However, Network A now is shown as an L con- 

 figuration having a series arm Z and a shunt admittance Y together with 

 an ideal transformer of ratio 1:K where K exceeds unity. Network A 

 of Fig. 9 is equivalent to Network A of Fig. 8, and Network B of Fig. 9 

 is the same as Network B of Fig. 8. In Fig. 9(b) the addition to this trans- 

 mission line of a single —Z such as the E2 repeater is shown. This nega- 

 tive impedance —Z cancels the series impedance Z of Network A. The 

 result is shown in Fig. 9(c). 



NETWORK A 



z z 



NETWORK B 



Zo 



I «.i+J/3i 



\^ TRANSMISSION LINE *\ 



(a) 



Zo- 



(c] 



Fig. 8 — ()|)or;iti()ii of the "T" in a Iransinissioii line: (a) transmission line, 

 1)) repeater and transmission line, and (e) result of addition of repeater. 



