On Sun, 28 Jun 2009 00:32:01 -0700 (PDT),
wrote:

So how would you determine if both transmitters are good

Spectrum analizer would be one way. Or even a scope capable of the
frequencies the remote transmitter uses might be viable.

or if
the receiver were good?

Test the transmitters, if they are good, then the receiver has failed.

Without being able to duplicate the modulation
scheme, the best I could do if I could determine the operating
frequency would be to hit this thing with a burst of CW from a signal
generator. I know that this would not operate the door but would it
disturb the onboard led

Unlikely to do anything.

thereby indicating the presence of RF being
received? How about if I take the transmitters and put them in close
proximity to my counter and if the transmission duration is long
enough I should be able to read the carrier? Lenny.

Maybe, if your counter is sensitive enough. Long shot, IMHO.

Do the manual buttons work? If yes, get a new receiver and you should
be happy: you will have the advantage of new security techniques that
were not available in 1992.