NEGATIVE IMPEDANCE TELEPHONE KEPEATEHS 



IOC)!) 



Thus Fig. 9 .shows that when a .single — Z is added in .series with the 

 conductors of a tran.smi.ssi()n line the attenuation is n^luced, hut the 

 e(|ui\-alent of a shunt conductance }' together with an impedance trans- 

 forniation is l(>ft. The impedance transformation ]:K could he cor- 

 rected hy means of a transform(M- if it were not for the shunt (element )'. 

 Thus an impedance irregularity is introduced, and this irregularity re- 

 lUx'ts power back toward the source. When the reflected power becomes 

 a significant part of the total power passing through the line, transmis- 

 sion is unsatisfactory. Echo is excessive and therefore the use of the 

 single series repeater is limited. 



THE BRIDGED T STRUCTURE 



The discussion of the T repeater, illustrated in P'ig. 8, was based on the 

 use of tw^o series negative impedances and a shunt negative admittance. 

 It is perfectly possible, and more economical, to obtain the same effect 

 by using a single .series impedance in a bridged T structure and this 



NETWORK A 

 Z 



NETWORK B 



UK 



Fig. 9 — Operation of —Z in a transmis.sion line: (a) transmission line, (b) 

 repeater and transmission line, and (c) result of adding repeater. 



