Acc position on key ignition?

For some reason the previous owner of my 88 TR wired the stereo directly to power... so I could potentially leave the radio on after turning the key off.

Question... how many positions does the TR starter switch have? I'm curious to know if it has four positions: (1) off (2) Acc on (3) Ignition on (4) starter engaged. Or does it just have three... without acc on and just ignition on. I seem to recall 4 positions, and my mechanic thinks there's only 3. I could be misinterpreting the positions when I turn the ignition key myself, and would like to know if anyone knows for sure.

Thanks! -Marc