Both the neck PU and the bridge PU may have their own independent switch, on top of the usual 3-way switch. The feature is found on several Artist models, be it the solid body AR series or the semi/full hollow body Artstar series. It was introduced in the late 70's (for example the Ibanez PF-300 in 1978 or the MC-300 in 1979), even though the wiring was quite different back in the days.