1092 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



measurement. When the return loss is positive, the unknown impedance 



contains positive resistance and the phase angle must lie between and 

 ±90 degrees. For negative return losses the unknown impedance con- 

 tains negative resistance and the phase angle must lie between ±90 

 degrees and 180 degrees. 



Acknowledgments 



The design of the E3 repeater was based upon theoretical work by 

 S. T. Meyers; the design of the test set was based upon theoretical work 

 by H. Kahl and S. T. Meyers. In regard to the theory of negative im- 

 pedances the contributions of F. B. Llewellyn are gratefully acknoTvl- 

 edged. 



REFERENCES 



1. J. L. Merrill, Jr., A Negative Impedance Repeater. A. I. E. E. Trans., 69, Part 



2, pp. 1461-1466; 1950. 



2. J. J. Pilliod, Fundamental Plans for Toll Telephone Plant, A. I. E. E. Trans. 



71, pp. 248-256. 



3. O. B. Blackwell, Time Factor in Telephone Transmission, A. I. 11. E. Trans., 



51, pp. 141-7. 



4. CI. Crisson, Negative Impedance and The Twin 21-Tvpe Repeater, B. S. T. .J., 



31, pp. 485-513, July, 1931. 



5. J. L. Merrill, Jr., Theory of The Negative Impedance Converter, B. S. T. J., 



51, pp. 88-109, Jan., 1951. 



6. W. E. Kahl and L. Pedersen, Some Design Features of the N-1 Carrier Tele- 



phone System, B. S. T. J., 51, pp. 418-446, April, 1951. 



