Is determined by the winding direction of a pickup either Top Coming or Top Going and how one or more coils are hooked up electrically. By reversing the beginning and finish wires in a coil will reverse the electrical phasing. By reversing the magnetic polarity of a magnet is called magnetic phasing. If two pickups have the same magnetic polarity (both South) and the coils are both wound and hooked up in the same way, the pickups will be electrically and magnetically in phase with each other. If one of the two coils is wound in an opposite direction each with the same magnetic field (both South) the pickups will be electrically out of phase etc.