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Letter: Letters: Round the twist

Published 30 April 1994

From JAN STUMPEL

Q: I have often observed defects, or knots, in helical telephone cords.
The areas to either side of the defect show opposite helicity (see figure).

Strangely enough, there is often only one such defect in the cord, although
two defects, enclosing one anomalous region, would be expected. It takes
a considerable effort to untangle the cord, which seems to be the only way
to restore uniform helicity.

How do these defects happen and how can they occur spontaneously during
normal handling of the telephone?

Jan Stumpel Tokyo

Issue no. 1923 published 30 April 1994

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