These most commonly use a pitot tube, with a total pressure side (moving airstream drives into holes facing the airstream) and a static pressure port. The detector is mounted in a chamber outside the duct. Air flows into one side of the chamber from the total pressure side, through the sealed chamber past the detector, and back into the duct through the static pressure port. Usually should be in an airstream moving faster than about 400 feet per minute.
1) Multi voltage - 24 volts dc, 24 volts ac, 120/1 volts ac power connections.
2) a big reset button.
3) remote reset terminals.
4) LON works chip.
5) battey back up option
6) automatic dust removal
7) self installing