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BELL SYSTEM TECHNICAL JOURNAL 



parts are separately shielded and symmetrically arranged so that the 

 assembly can be attached to a portable balanced oscillator used for 

 other work. Such a combination is shown in the photograph of Fig. 1 7 . 

 Again referring to Fig. 16, the condensers marked Ci control the 

 degree of coupling while maintaining an accurate balance to ground. 



Fig. 17 — Impedance measuring equipment and balanced oscillator. 



C'l is a condenser used for anti-resonating the complete circuit, this 

 anti-resonance being indicated by a thermocouple deflection. The 

 condensers labelled Cz are large blocking condensers which have been 

 added to the circuit to permit the measurement of the value of the 

 variable substitution resistance without the necessity of disconnecting 

 that resistance. A pencil lead is usually employed as this resistor. 



