Ongoing CF discussion:Dimmable

[Rob Lewis]

Speaking of CFs and dimming, perhaps somebody can solve this puzzler:

We have a couple of bedside lamps. They came with cord-mounted  
switches: the little wheels that you turn to click on and off. Only  
these go Off-Dim-Bright-Off. I've never seen this before and was  
unable to find a replacement when mine burned out (so I used the  
standard Off-On-Off type).

My wife's still works, however. Recently she installed a CFL in the  
lamp to save energy. When she told me I thought, that will be  
interesting to see how a CFL works with the dimming switch.

I always assumed that these 2-level switches worked by inserting a  
diode to half-wave-rectify the AC in the Dim position, but I don't  
really know.

Anyway, the surprising thing is that the CFL works--at full  
brightness--in both the Bright and Dim positions of the switch.

Anybody have a clue what's going on here?