Jethro wrote:
An acquaintance at yesterday's neighborhood picnic asked me if I could
help him with a problem. He said his opener (make unknown right now
until he calls me to tell me) has stopped working. He bought a pair
of new Genie sensors at HD, but they didn't help. He said one lights
red okay, but the other does not light green. He called Genie and
they said you cannot use Genie sensors with other makes.

Is this true? Or, in other words, are sensors interchangeable, or can
you only use sensors on an opener of the same make? I

Unless his opener was also made by Genie, it's true because the each
manufacturer's sensor system uses somewhat elaborate pulsating optical
and electrical signals for its sensors, both to prevent false
triggering and to keep people from bypassing the safety system easily,
and the industry never agreed on a single standard for each.. Also
some openers have the sensors and wall button tied to the same wiring
and therefore are particular about DC voltage levels as well (this has
caused problems for Chamberlain/Liftmaster/Sears systems -- sometimes
the door could be closed even when the optical beam was blocked).