I believe it's 12v - I've got a wiring diagram around here somewhere that was sent to me by a VX owner in FL (not on the list - met him by accident during the N. GA/TN meet up on Black Rock Mountain way back) - anyway, he owned a shop and had wired it just so - sent me a scan of a drawing much like yours but it showed how you could use the relay to disable the popper switch unless the VX was in park. I've never accidently hit mine but I could see how it could happen while driving. I'll see if I can find that scan.
-- John