That name came from the method wires were joined back when the telegraph was the state of the art method of long distance communication. Since most telegraph lines were single-conductor solid wire, the tightly twisted splice made a low-resistance connection that was mechanically stronger than the wire itself. Put a hard pull on a properly-wrapped WU splice, and the wire will break before the splice unwraps itself. The same type of joint is very effective when stringing long runs of barbed wire fencing.

https://cdn.instructables.com/F1R/7USF/IRLQLLP6/F1R7USFIRLQLLP6.MEDIUM.jpg

To simply tap a connection off a long run of wire, just strip the insulation off without cutting the wire and wrap the branch circuit tightly around the main conductor.
Jerry




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