@2ck Looks like the old sign that basically shows 'deaf-mute'. Dutch sign language uses that too. But the universal sign nowadays is really tapping the ear once with a scout hand shape I've noticed. Or as I'd like to show to hearing people, tapping my ear twice and shrugging and shaking my head. Kinda hard to miss that one. ;)
@2ck ASL and NGT (Dutch Sign Language) have LSF as their root (Le Sign France), so there's somewhat an overlap there at the basis, including fingerspelling. Not 100%, mind you, but still.. somewhat. International Sign (kinda like Esperanto, lol) has a HUGE overlap with those. If you know ASL, you tend to have an easier time getting to know IS.
BSL.. well we know the British like to be opposite of everything, especially Frenchies, and they thought they knew it better and fabricated their own sign language. Bloody annoying, if you ask me. :P Yes, it's totally different.
I know ASL and NGT, and can understand large parts of IS.