I have a problem where I want to have 6 switches controlling four lines. Each switch drives two lines high, each seperate switch drives a different combination of two lines. So if I have four lines labelled A through D, each switch would do the following:
1 AB
2 AC
3 AD
4 BC
5 BD
6 CD

The problem comes that if you wire the switches up like this, all four lines will be connected together. You could overcome this with a double pole double throw switch (or is there another switch that has one common line on one side and two on the other?) you'd tie the two poles on one side of the switch to your voltage source and each of the other two poles to one line each.
eg:

Code:

Vcc --- SWITCH --- A
Vcc --- SWITCH --- B

However, I haven't been able to find tiny DPDT switches, so I have a bunch of SPST switches which are of perfect size. The only way I know how to solve this problem is to use a bunch of diodes, so I'd have

Code:

Vcc --- SWITCH --- diode to A
               --- diode to B

This solution would work for me, but I'd end up with 12 diodes and I'm trying to keep the size (and complexity) of the circuit to a minimum as it's to be a keyfob sized transmitter...can anyone think of another way to implement this with SPST switches? If I were to have to use a 12pin or larger IC, I might as well use the diodes as they'd be around the same size.

With individual switches what happens if two are ON at the same time? It seems to me this requires a 6 position rotary switch or a set of push-switches where pusing one releses the others.

If you resign yourself that you will need a chip, a simple microcontroller would be easy. John

The simplest standard logic circuit I could think of to work with SPDT switches uses 4 triple-input OR gates. But that would require 2 chips since I think the most available on one chip is 3 gates.

Ah wow, I like that solution john1, I went ahead and made a PCB for the prototype (which will probably end up being the production model as I'm only planning on making one unless is breaks) using 12 diodes, but I'll keep your drawing in mind if I make it again (or anything similar in the future). I know I have a few SPDT switches that I salvaged, I think they came from computer mouses (mice?). Most of my tiny switches are SPST though.

Ooops, looking at the drawing again I see that multiple switches might have to be simultaneously pushed to get the outputs, in which case singly wiring each switch to an output would have the same results. Am looking to press a single button to get the desired output.