Some of us, not even that. Just hobbyists.
Typically, well-grounded in the practical, however.
And, I dunno, our neighbor has a garage door with a floor switch tied to hi s home-security system. It indicates on his keypad, and if he tries to arm with it open, it announces "Garage Door Open". I expect that two inches ope n = Open, but were I to bother with garage doors, I would want to know if it were open even a little bit.
Point being that this is an off-the-shelf device
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Or, even one of those automated doorbells that rings several hundred feet a way when a door opens.
No muss, no fuss.
Peter Wieck Melrose Park, PA