In light of Schumacher's DRS failure I've been thinking about this.
So obviously the DRS hydraulics (or is it motorised?) are strong enough to pull the DRS flap up at even max downforce positions, or at the very least - right on the exit of the quickest corner in F1. Whatever that corner is.
So with the system being stronger than the drag/downforce the flap produces at said velocity - how exactly is the failsafe mode engaged? How does the system detect a failure of DRS, and proceed to release the flap? Is it some sort of mechanical failsafe, or electronic? Is it in the regs?