>Ok, we have two lamps that act like this:
>

>Click
>Click
>Click (on)
>Click
>Click
>Click (off)
>

>I figured since there were extra clicks - albeit not the right number, but more than just on/off - that they must be 3-way lamps. When I put a 3-way bulb into them, they do not work like I expected, but just like they did before with a standard bulb. Why do the lamps have extra clicks if they are not 3-way, or why do they not work with a 3-way bulb if they are?
>
>There is a domestic dispute regarding this, so any information is gladly appreciated.

Sometimes switches like that are used to control multiple bulbs on track or pole lighting. However, I can't think why there would be 6 switch positions. For example:

2 bulbs: both off/#1 on/#2 on/both on ==> 4 positions

3 bulbs: all off/#1 on/#2 on/#3 on/#s 1 and 2 on/#s 2 and 3 on/#s 1 and 3 on/all on ==> 8 positions

If a couple of the modes for 3 bulbs were not supported/implemented, that might account for 6 positions.

Thinking about dual-filament ("3-way") bulbs, there are actually 2 possible types:

- "Type 1": one filament is "larger" than the other. Suppose one of them was 50W, and the other 100W. This bulb could then support 0W/50W/100W/150W combinations

- "Type 2": both filaments are the same "size". If both were 50W, then the bulb would support 0W/50W/100W combinations

Combination of 1 standard bulb + 1 Type 2 dual-filament bulb:
Std Dual
---------------
Off Off
Off Low
Off High
On Off
On Low
On High

Sometimes you see chandeliers and other complex fixtures with a central dual-filament bulb, plus surrounding bulb(s) that are standard bulbs.