292 BELL SYSTEM TECHNICAL JOURNAL 



it is always possible to measure off N and L and the angle between them, 

 spot the complex ratio L/N on the complex plane and read immediately the 

 approximate return loss. 



Conclusion 



The examples of the foregoing discussion have been confined to the fourth 

 quadrant. It was shown that by graphical means a number of parallel 

 resistance-condenser functions could be determined which when added 

 together would yield a close approximation to the given function. In the 

 most general case these functions would involve the generating function of 

 R, L and C in parallel, the locus of which is a circle having impedance 

 +7O at zero frequency and — 7O at infinite frequency, and crossing the axis of 

 reals at R and the frequency at which L and C are anti-resonant. A case 

 which has been found useful in simulating such things as telephone sets and 

 other inductive elements is the parallel combination of R and L which, of 

 course, is the special case for C = and occurs in the first quadrant. 



The foregoing has been discussed with the thought that it may be useful 

 where there is limited time and where the required degree of simulation 

 is consistent with a graphical method. At some future time it may be 

 possible to pursue the problem further and devise the analytic counterpart 

 to the somewhat heuristic graphical method. 



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