Re: Flourescent Dimmers
What do you mean by a "R-lamp" George? Is this an incandescant can light with a fluorescent lamp installed??
All fluorescent lamps need a ballast. (If they are the new compact kind you install in an incandescent fixture, they have the ballast built right into the lamp housing).
In general, a ballast is made to regulate the power to the lamp (and the light output). So if you just vary the input voltage to the ballast, it will normally try to compensate by boosting the output current. So just varying the input voltage to the ballast doesn't work like varying the voltage to an incandescent lamp would work. That's why I say the ballast does the dimming, and the switch just tells it how much power to put out.
There may be a few fluorescent lamp-ballast combinations that don't fit this description, but I think most do.
As a side note, I have seen people run a fluorecent ballast from a regular dimmer switch. It does work (at least sometimes), but you don't get a very good range, it's hard to adjust, and the lamp doesn't start in a reliable way. In effect, you get something that might half work.
Steve