Over at the sister-in-law's last weekend, noticed a ceiling fixture was dark and volunteered to put in a new bulb, hero that I am. While putting in the new bulb I noticed that the lighted switch that controls the ceiling fixture went on (i.e. lit up). Indeed, bulb unscrewed - switch's light out; bulb in - switch's light on. Come to think of it, the switch's light hadn't been on before when the burned- out bulb was in the fixture.
In short, it seems the switch's light is wired in series with the fixture. Is that how it's supposed to be? Does that serve some purpose? Just curious -- H