which type of DPDT toggle switch do I need?

[powerplayj]

1   2   3             input -> 2

4   5   6             output -> 5

I basically want to swicth between 3 resistor values with resistors between 1-4, 2-5 and 3-6.  (2-5) will be the lowest value and the midddle switch position while moving the switch to the right or left will add resistors (1-4 or 3-6) in parallel.  I think I need an On-On DPDT toggle but I'm confused as to what the difference is between an On-On and an On-Off-On.   Any help would be appreciated...........

[twabelljr]

    You need on-off-on to be able to add 1/4 and 3/6 in parallel with 2/5. 2/5 will be the center lug (off). An on-on switch would not allow the use of 2/5 by itself, because it does not have a center position.
Edit: 2/5 should be the highest value resistance. Then you add resistance in parallel for lower values.

[powerplayj]

Thanks.....

highest resistance at 2-5?  Can you explain the reasoning please?  I was initially thinking 1k, 500k and 1M with the 1k at 2-5, a 1M at 1-4 and a 2M at 3-6?

[twabelljr]

Using a parallel resistor calculator you should us a 1k at 1/4, a 1meg at 5/2, and a 1meg at 3/6. Then you achieve 1M with 5/2. 500k with 3/6 switched in, and 1k with 1/4 switched in. There are probably some other ways to get the same results. Here's the calculator I used:
                          http://www.diystompboxes.com/analogalchemy/emh/emh.html