response 12 of 15:

Jan 30 04:53 UTC 2006

Re resp:11: I think that's essentially correct.  There's also a window 
of codes the opener will allow, in case the button was pressed a few 
times when the remote was out of range of the opener. I believe there's 
some kind of failsafe mechanism to get the opener and the remote back 
in sync if they get way apart, as well, but I don't remember how it 
works.  There were details reported back when there was that DMCA 
lawsuit about aftermarket opener remotes.  These systems are 
proprietary, of course, and vary from manufacturer to manufacturer. 
 
The idea of having a rotating feature in the code is so that simply 
recording and replaying the transmission won't open the door. 
 

response 14 of 15:

Jan 31 07:00 UTC 2006

I can't recall how the re-synchronization feature of the protocal 
worked.  I think it may have simply been triggered by a certain number 
of invalid transmissions, like would happen from holding the button 
down longer than usual because it wasn't working.  I do recall it 
formed the security loophole that the company in question was using to 
make third-party, aftermarket remotes for a popular line of openers, 
and this is what got them sued under the DMCA.