. The Bell System technical journal . ion effect could usually be esti-mated with sufficient accuracy by calculating the crosstalk from a toc and back again and neglecting the further reactions of the changein the current in a on the current in c, etc. 1 OPEN-WIRE CROSSTALK 33 Figure 7 shows the crosstalk paths from a to c and back this figure, circuit a is indicated as two separate circuits for com-parison with Fig. 2B. It is assumed that circuit a in Fig. 7 is energizedat point A, the currents J a and Ib being the currents which wouldexist at the input and output of the short length
. The Bell System technical journal . ion effect could usually be esti-mated with sufficient accuracy by calculating the crosstalk from a toc and back again and neglecting the further reactions of the changein the current in a on the current in c, etc. 1 OPEN-WIRE CROSSTALK 33 Figure 7 shows the crosstalk paths from a to c and back this figure, circuit a is indicated as two separate circuits for com-parison with Fig. 2B. It is assumed that circuit a in Fig. 7 is energizedat point A, the currents J a and Ib being the currents which wouldexist at the input and output of the short length d if there were notertiary circuits. The near-end crosstalk path indicated by n willcause a small crosstalk current in at point A in circuit a. There willbe a crosstalk path similar to n in each thin slice of the parallel betweena and c. Each of these paths will transmit a small crosstalk currentto point A in circuit a. The sum of all these crosstalk currents willincrease the input current Ia and, therefore, the impedance of circuit. r TO LONG CIRCUITS i Fig. 7—Effect of circuit c on propagation in circuit a. a is lowered. Thin slices remote from the sending end will contributelittle to this effect, since the crosstalk currents from such slices will beattenuated to negligible proportions. A long circuit on a multi-wireline will, therefore, have a definite sending-end impedance slightlylower than that for one circuit alone on the line. Figure 7 also indicates a far-end crosstalk path / which produces acrosstalk current if at point B in circuit a. This reduces the trans-mission current Ib at this point and, therefore, increases the attenu-ation constant of the circuit. For calculations of both the circuit 34 BELL SYSTEM TECHNICAL JOURNAL impedance and attenuation, the effect of surrounding circuits is takencare of in practice by using a capacity per unit length sHghtly higherthan the value which would exist with only one circuit on the proper capacity to use is determ
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