Okay:
There are three light bulbs on the 2nd floor of a building and there are three switches on the ground floor which are used to turn on the light bulbs (one switch for each bulb). A man is on the ground floor knows that all the light bulbs are turned off. How can he just go up the 2nd floor once and determine which switches turn on which light?
By the way, dave, is your name "Chocobojoe" on anther website?