For those interested, wiki as always has a lot of copy and pasted from text books information. http://en.wikipedia.org/wiki/Spin_%28physics%29
Technically, spin applies to individual particles, not field effects, so Doc isn’t really using the term correctly. However, a particle with spin of zero means that for all intents and purposes it is infinitely symmetrical, that is, it’s the exact same when viewed from any angle. (think of old 3d games where most “objects” were a flat 2d image that always moved to face you as you moved.)
in this case it means that the field effect created by the device is identical in every direction at all times, so spinning the field SHOULDN’T do anything different.