Without knowing which chassis you have, or which brand of slides you have, I'd only be guessing, but probably there's a 4"X4"X2" box under the dash on the drivers side on the firewall, covered by large bundles of wires.
Yes, there are interlocks and it depends on the RV manufacturer how they did theirs but all of them prevent you from driving somehow if the slide is extended AND they prevent the operation of the slides if the brake is not set. Oh, and the jacks too. I don't know about a drivers seat interlock but it's possible of course if the RV slide would ruin the seat if you retracted the slide with the seat set too far back. Most don't bother with an interlock like that thou.