Crosstalk on Open-Wire Lines 



By W. C. BABCOCK, ESTHER RENTROP, and C. S. THAELER 



(Manuscript received September 29, 1955) 



Crosstalk on open-wire lines results from cross-induction between the 

 circuits due to the electric and magnetic fields surrounding the wires. 

 The limitation of crosstalk couplings to tolerable magnitudes is achieved 

 by systematically turning over or transposing the conductors that 

 comprise the circuits. The fundamental theory underlying the engineer- 

 ing of such transposition arrangements was presented by A. G. Chapman 

 in a paper entitled Open-Wire Crosstalk published in the Bell System 

 Technical Journal in January and April, 1934. 



There is now available a Monograph (No. 2520) supplementing Mr. 

 Chapman's paper which reflects a considerable amount of experience re- 

 sulting from the application of these techniques and provides a basis for 

 the engineering of open-wire plant. The scope of the material is indi- 

 cated by the following: 



TRANSPOSITION PATTERNS 



This describes the basic transposition types which define the number 

 and locations of transpositions applied to the individual open-wire 

 circuits. 



TYPES OF CROSSTALK COUPLING 



Crosstalk occurs both within incremental segments of line and be- 

 tween such segments. Furthermore, the coupling may result from cross- 

 induction directly from a disturbing to a disturbed circuit or indirectly 

 by way of an intervening tertiary circuit. On the disturbed circuit the 

 crosstalk is propagated both toward the source of the original signal 

 and toward the distant terminal. A knowledge of the relative importance 

 of the various types of coupling is valuable in establishing certain time- 

 saving approximations which facilitate the analysis of the total cross- 

 talk picture. 



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