When Leo Fender shipped the very first solidbody guitar, which we know today as the Telecaster, the two pickups were selected by means of a 3-position blade switch, with a large, black “top hat” tip. You would flip it forward to access the neck pickup and backward to access the bridge pickup. When Leo shipped his new upscale Stratocaster a few years later, it also had a 3-way blade switch, despite the fact that the Strat had an extra pickup. Those early Strat blade switches gave you access to the bridge, middle or neck pickups separately. It wasn’t until a few guitarists tinkered around and hit upon the trick of lodging the blade switch in the “in-between” positions that the Strat became famous for its “out-of-phase” sounds (which weren’t actually electronically out-of-phase – though there are phase differences in the string motion sensed by each pickup – but sounded so unusual that the designation stuck). Eventually Fender upgraded the Strat to include a 5-position blade switch, which made it much easier to access the “in-between” pickup combinations. More recently, the middle pickup has been wired in a true out-of-phase fashion, with the polarity reversed, to cut down on hum problems.