a twisted pair

Take the two wires of a signal, the one carrying it out and the one carrying it back, and twist them together into a tight spiral. That simple, cheap trick is a twisted pair, and it is one of the most effective noise defences ever invented. It is why Ethernet and telephone lines are twisted pairs rather than straight wires: the twist makes the cable shrug off magnetic interference and lets the receiver reject hum that the two wires pick up together.

Two effects do the work. First, twisting nearly eliminates the loop area between the wires, so there is almost no open loop for a magnetic field to push current around, and magnetic pickup, which depends on loop area, collapses toward zero. Second, because the two wires run together, any interference reaches both of them almost identically, as a common-mode voltage; a differential receiver looks only at the DIFFERENCE between the wires and subtracts that shared noise away (common-mode rejection). The twist also rotates the wires, so whatever flux does sneak into one half-twist is cancelled by the oppositely-oriented next half-twist.

Twisted pair plus differential signalling is the standard way to send a clean signal across a noisy distance, used everywhere from balanced microphone cables (XLR) to USB, Ethernet, and the CAN bus. Honest limits: the cancellation is only as good as the balance of the two wires and the receiver's common-mode rejection ratio, and twisting helps against MAGNETIC coupling far more than against a strong nearby ELECTRIC field. For the electric part you add a grounded shield around the pair (shielded twisted pair). Twist defeats magnetic pickup, shield defeats electric pickup, and together they are formidable.