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BELL SYSTEM TECHNICAL JOURNAL 



Fig. 2 gives all of the combinations of fixed arms which meet the 

 phase angle requirements already stated, when limited to simple 

 resistance, inductance, or capacitance. For all forms, the magnitude 

 of one arm is given in terms of the other and of a constant K, such 



(e) (f) 



2 RATIO ARM TYPE e = GaB" ^BC =±9°' 



D 



(9) 



(h) (I) 



3 PRODUCT ARM TYPE 



e = eAD +eBc = o° 



D 

 (j) (K) 



4 PRODUCT ARM TYPE 



e = eAD + eBc = ±9o° 



Fig. 2 — The various forms of 4-arm bridges divided into four types. Forms 

 f, g and j are impractical. 



that the only term which appears in the balance equation is the term K. 

 None of these bridges represents a distinctly new type, but since the 

 classification is by means of the fixed impedance arms, one of them 

 may be used to measure several types of impedance. Accordingly, it 

 may correspond to more than one of the well-known bridge types. 



