Anyone know about the connections for the wired switch that operates a
(probably) Chamberlain garage door opener? Going to help a friend with
some tasks at the w/e and one of the things he'd like to do is install
a new bellpush to open the garage door from inside the house. There's
a wired switch inside the garage. This has 3 buttons (open/close,
light, disable remote) but only single bell wire linking to the unit.
So what differentiates the functions (timing of current applied?) /
how to replicate just the open function.

Forgive the vagueness but I've not seen this setup yet and want to be
prepared / not waste time playing around or stuffing up the unit.

Ta muchly
B.