232 



BELL SYSTEM TECIIMCAL JOLRXAL 



Equation (?>) is derived in the ai)pendix and plotted for several values Ai/- 

 in Fig. 8. 



The phase bridge essentially converts the measurement of phase into the 

 measurement of voltage diflference. \'acuum tube diodes are used as dif- 



20 LOG -r^ 



Fis;. 7 — Deflection response of the phase bridge. 



10 15 20 26 JO 35 40 45 50 55 60 



DEPARTURE,!", OF E, AND Ej FROM QUADRATURE 



Fig. 8 — Phase error A\t for unequal inputs. 



ferential rectifiers with a high resistance load consisting of hermetically 

 sealed carbon deposited resistors closely matched for value and temperature 

 coefficient and specially mounted to minimize temperature diflFerentials. 

 The dififerential output of the rectifiers is amplified in a feedback stabilized 



