. The Bell System technical journal . Fig. 21—Point-type transposition. illustrated by Fig. 22 is considerably cheaper but the displacement ofthe wires is much greater. The effect of this displacement is importantand must be especially considered in transposition design. If all the spans adjacent to a drop bracket were of the same length. O© Fig. 22—Drop-bracket transposition. 206 BELL SYSTEM TECHNICAL JOURNAL and all wires could be kept under the same tension, the effect of dropbrackets on crosstalk would be consistent and could, theoretically, bemade negligible by a suitable transposition de
. The Bell System technical journal . Fig. 21—Point-type transposition. illustrated by Fig. 22 is considerably cheaper but the displacement ofthe wires is much greater. The effect of this displacement is importantand must be especially considered in transposition design. If all the spans adjacent to a drop bracket were of the same length. O© Fig. 22—Drop-bracket transposition. 206 BELL SYSTEM TECHNICAL JOURNAL and all wires could be kept under the same tension, the effect of dropbrackets on crosstalk would be consistent and could, theoretically, bemade negligible by a suitable transposition design. There is, however, an accidental crosstalk effect. This effect ispartly due to the fact that it is more difficult to avoid deviations fromnormal sag in the spans adjacent to drop brackets than in normal main effect, however, is thought to be due to inequalities in thelengths of the spans adjacent to drop brackets. The crosstalk in such a span is very nearly proportional to thelength of the span times a constant or equivalent crosstalk coeffi-cient. The usual crosstalk coefficient can not be used because thewires are not parallel. Fig. 23-A indicates two long circuits, one circuit being transposedon drop brackets at the first and third quarter points of the shortlength D. The lengths of the spans adjacent to the
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
