I guess it depends. There's probably different types for different applications. I think most will come with some form of detent, some might have "configurable" setups where multiple encoders and/or detents can be stacked on a single shaft, and some will be free of detents to be used as a jog wheel. The fact you are mentioning just two pins (plus ground, I figure) for a 12 positions encoder makes me think that this will be a relative position encoder, like that used in a mousewheel (incidentally my
Logitech G700 has a button to toggle detents). This means that there won't be an absolute zero position. To get 12 steps of resolution with a standard binary or gray encoder you need 4 pins, one per bit (0000 to 1100), but an encoder would probably give you the full 16 steps. You could wire a binary encoder through an R-2R ladder to be read through an analog channel, though, if it's based on electrical contacts, and you could do the same with a resistor network on a rotary switch. that would use just one pin, and a bit more logic anc cycles.