"Then if someone like a parking lot attendent had access to a
sophisticated storage ocilliscope/spectrum analyzer/function
generator, couldn't they just press the button once and have their
device learn a valid code?
As long as they used it before the owner went back home (say by
telephoning the code to an accomplice), then they would have access to
the garage, right?
Not that your average Joe thief would have access to this kind of
equipment, but the rotating code scheme doesn't seem to provide the
degree of security that it promises.... "
Yes, I believe that would work. If they pressed the button on your
transmitter while they had access to your car, captured the transmitted
digital code, went to your house and retransmitted that code to the
opener before you returned and used the transmitter yourself, it should
work. Of course to do that would take a hell of a lot of fairly
sophisticated equipment and there are much easier ways to gain entry to
garages. Most alarm systems don't even cover the garage area. Plus,
if you allow someone access to the transmitter, they could also just
use that by taking it over to the house and skip all the hitech stuff!