I'm looking at building my own decade resistance box, but the typical rotary switches are... quite expensive. They seem to be the most expensive part of the entire project. Whether I choose a [real rotary switch](http://www.digikey.com/product-search/en?pv88=10&pv832=2&pv833=1&FV=fff40011%2Cfff80062&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25) or a [DIP switch](http://www.digikey.com/product-search/en?pv130=128&FV=fff40011%2Cfff8005b%2C160000a&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25) or even a [thumbwheel switch](http://www.digikey.com/product-search/en?pv446=1&FV=fff40011%2Cfff80502%2C6fc0001&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25), the standard decade resistance box uses an SP10T switch that is either expensive or limited in selection.

I've seen a lot more switches that use a BCD output code, or a BCD complement code (example: [page six of this datasheet, specifically switch functions 1 and 2](http://www.ck-components.com/13309/rte_11mar10.pdf/). But I'm having a tough time wrapping my head around the connections. In an SP10T switch, you connect the 0 terminal to the "input", and the common terminal is the "output" (or vice versa), as seen here:
![credit to eevblog 212](https://puu.sh/4tjC8/f7d7d154e0.png)
(source: EEVblog #212)

But a BCD switch makes multiple connections depending on the desired code. For example, if I set the switch to 3, then the common terminal will be shorted to positions 1 *and* 2. In a BCD-complement switch, if I set the switch to 3, then the common terminal is shorted to positions 4 and 8. Either way, I can't come up with an arrangement of resistors that would yield a resistance of 3ohms (or 30, or 300, etc).
This is the switch function diagram for the switches I have in mind, which might be a clearer explanation of the behavior I'm describing:
![c&k datasheet](https://puu.sh/4tmFY/535dce8702.png)

Sorry if this question is kind of confusing, I'm having a hard time explaining it myself! To summarize, does anyone have a connection diagram for a decade resistance box using BCD switches?