Over/under cable coiling
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Over/under cable coiling refers to a method of storing cables that preserves the capacitance and common-mode rejection ratio built in by the manufacturer with a twist in the cable, and the shielding that encases the twisted pairs within. It allows the cable to lie flat when uncoiled, and makes for easier and faster work.
The "over/under" name refers to the practice of twisting the cable in one direction to make the first coil, and un-twisting it to make the next, and repeating this until all the cable is neatly coiled. Care needs to be taken to keep each end on its proper side of the roll when uncoiling otherwise a knot will appear with every other loop. Connecting the ends on the outside of the loops, or tying them in that position, ensures that the ends don't pass through the loops in storage so there are no knots when the cable is laid out.
The alternative: straight coiling
Straight coiling or the practice of coiling a cable in the same direction coil after coil, has the similar result to coiling cable on a spool. If the cable comes off the spool the same way it goes on, the internal 'lay' is preserved, and the cable isn't damaged or become twisted internally. If a cable is straight coiled and then pulled from the coil, it has the effect as coiling cable on a spool and then pulling the cable off the top of the spool, imparting a twist in the cable with every coil that is removed. To make it lay flat the twist will need to be removed. The only advantages of straight coiling cable are that it will not produce knots when uncoiling and is easily taught and therefore can be accomplished by untrained assistance. It will, however, shorten the useful life of a cable, and erode its noise-rejection properties.
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