Inductive coupling - fixing by using coaxial cable
Coaxial cable has the property of producing no magnetic field external to the cable because in the region outside the cable the return (shield) conductor, being coaxial with the signal conductor, produces a magnetic field equal and opposite to that produced by the signal conductor. Thus, if coaxial cable is used, no magnetic field is produced that could link another circuit. Caox can be used on the signal circuit to make it immune from stray fields and on other circuits to prevent them from producing stray fields. The immunity of the signal circuit can be seen in Fig. 9 by considering imaginary surfaces (dashed lines) on either side of the center conductor with a cut in the outer conductor. If the coax in Fig. 9 is unrolled, then the direction of the two surfaces (indicated by small black arrows) are opposite so any external magnetic field (blue lines) penetrating the coax produces no net flux.