Dan,
It would seem to me that you would want "active high" until tripped. Otherwise, if power connection to the circuit fails, you have the same problem as a NO switch. You can't tell until the switch is tripped that it is not working. You don't know whether it is "low" because the switch is closed or "low" because power to the circuit has failed.
Alan
__________________
http://www.alansmachineworks.com |