Thanks Chris.

I think I've got it figured out. An OPEN garage door CLOSES the curcuit in a magnetic switch leading to the input leads on an X10 PUM01. When that PUM01 gets a timed command to activate it will only do so if the switch circuit is CLOSED, or complete. In activation it CLOSES the garage door button circuit, closing the door.

If I missed something, don't worry. There's nothing in my garage to steal.