You and 5 unfortunates are [to be] locked up [somewhere]. You all know that there is a single toggle switch initially in the UP position[,] to be found in a special room. Prisoners are kept apart and cannot communicate once the [period of imprisonment] starts. Prisoners are taken from their solitary cells one by one and one at a time, in no [particular] order, to this control room.
The only way out... is if one of you declares correctly that all of you have visited the room at least once. The downside is that you will [all] stay there [forever] if the statement when uttered is made incorrectly. You have a few moments together before the [period of imprisonment] starts[,] to set up a strategy. No one else may interfere with the room. How can you arrange for one of you to be in a position to know that 'we have all of us visited the room at least once'?
I don't wish to spoil Norm's fun, so am not going to post my solution here without his permission. I have emailed my solution to him, however, and I'm sure he'll get me a knighthood or something as acknowledgement.
See? I was right. I redirect your attention to the title of this post.