Image Stabilization question on Canon with tripod

I recently purchased a Canon 70-300mm IS USM lens. In all the
literature it states that the Image Stabilization is 'automatically'
turned off when the camera+lens is mounted on a tripod. My question is,
how does the lens know it is mounted on a tripod? Is it something to do
with the motion-sensors in the lens ? Or, is there some sort of
feedback from the tripod socket itself ? (I notice that there is a pin
in the bottom of the camera tripod socket) If this pin is actually a
switch which turns off IS, then does it turn off every time I screw
something (like a hand grip or flash bracket) into the tripod socket
????

"KayakerBob" wrote in message
ps.com...
I recently purchased a Canon 70-300mm IS USM lens. In all the
literature it states that the Image Stabilization is 'automatically'
turned off when the camera+lens is mounted on a tripod. My question is,
how does the lens know it is mounted on a tripod? Is it something to do
with the motion-sensors in the lens ? Or, is there some sort of
feedback from the tripod socket itself ? (I notice that there is a pin
in the bottom of the camera tripod socket) If this pin is actually a
switch which turns off IS, then does it turn off every time I screw
something (like a hand grip or flash bracket) into the tripod socket
????

No. I don't know how the IS knows that the camera is tripod mounted, but the
pin in the hot shoe has nothing to do with it. The pin is to make sure you
have the threaded hold down well loosened before you attempt to remove the
camera, so you don't short out the hot shoe contacts for any appreciable
length of time.