220 BELL S YSTEM TECH NIC A L JOURNA L 



resistance Rx located in the series branch may be evaluated from the ex- 

 pression 



t 



in which t is the transfer loss in nepers at the critical frequency, R is the 

 135 ohm resistance termination and Rdc is the DC resistance of the induc- 

 tance coil. The resistance Ry located in parallel with the series resonant 



R} 



branch may be evaluated from the expression Ry = -^ . 



Rx 



By changing the loss, e , of the derived resistance pad at zero frequency 

 slightly from the measured loss at the critical frequency of the delay section, 

 a suitable loss compensation may be realized to produce an optimum loss 

 equalization over the message and program channel ranges. It is satis- 

 factory to follow this technique when the condenser Q factor is much greater 

 than the coil Q factor. When this condition exists, the insertion loss about 

 the critical frequency becomes geometrically dissymmetrical, that is, the 

 loss falls off more rapidly for frequencies above the critical frequency be- 

 cause of the controlling condenser Q factor. 



References 



1. "A Carrier System for 8000-Cycle Program Transmission," R. A. Leconte, D. B. 



Penick, C. VV. Schramm, A. J. Wier., a companion paper. This issue of BSTJ. 



2. "Electromechanical Transducers and Wave Filters" (book), W. P. Mason, D. Van 



Nostrand Co., New York, N. Y., 1942. 



3. "Delay Equalization of 8-kc Carrier Program Circuits," C. H. Dagnall and P. W. 



Rounds, a companion paper. This issue of BSTJ. 



4. "Communication Networks," Vol. II (book), E. A. Guillemin, John Wiley & Sons, 



New York, N. Y., 1935. 



5. "The Mounting and Fabrication of Plated Quartz Crystal Units," R. M. C. Greenidge, 



Bell Sys. Tech. Jour., Vol. 23, July 1944, page 234. 



6. "A New Crystal Channel Filter for Broad Band Carrier Systems," E. S. Willis, 



Elec. Eng., Vol. 65, March 1946, Page 134. 



7. "Theory and Design of Uniform and Composite Electric Wave Filters," O. J. Zobel, 



Bell Sys. Tech. Jour., Vol. 2, 1923, Pages 1-46. 



8. "Synthesis of Reactance 4-Poles which Produce Prescribed Insertion Loss Charac- 



teristics," S. Darlington, Journal of Mathematics and Physics, Vol. 18, No. 4, Sept. 

 1939. 



9. "Ein Interpolationsproblem mit Funktionen mit Positiven Realteil," W. Cauer, 



Mathematische Zeitschrift, 38, 1-44, 1933. 

 10. "Distortion Correction in Electrical Circuits with Constant Resistance Recurrent 

 Networks," O. J. Zobel, Bell Sys. Tech. Jour., Vol. 7, July 1928, Pages 438-534. 



