Look AST - how does it work?

[MnO]

Just picked up a old Look TT09 Racing din 7-15. The binding looks nice and seems to works really good, but what the heck is the function of the plastic AST slider on the side of the toe piece? I took out the spring and removed the rubber piece to try the function, but it just seems like total nonsense. What is the AST supposed to do?

I know that it might have been up on the forum before, but I really tried to find something with the search function and spend half an hour finding nothing.

[mntlion]

one possition it is upward release, other way it doesn't

PM waxman or L7, they might remember..