ACSI 1335-3 Door Position 1" Recessed mount, SPDT, NO/NC contacts

It's a two-piece magnetic contact. The sensor body mounts in the frame and a magnet mounts in the door; when the door swings shut, the magnet comes into proximity with the sensor and the contacts change state. No mechanical plunger to wear out, and nothing touches when the door closes.

Yes. The 1335-3 is SPDT with both NO and NC contacts, so you have a common plus both a normally open and a normally closed leg. That lets you wire it either way depending on whether your panel or annunciator wants the circuit to make or break on door open, and it means one device can serve a supervised loop or a simple status input without swapping hardware.

No. The 1335-3 is an electrical magnetic contact. ACSI builds pneumatic models in the 1335 Door Position Sensor family for hazardous locations, and that is what you should be specifying where an electrical contact isn't permitted.

The 1335 Door Position Sensor is a sensor-and-magnet pair by design: the magnetic sensor goes in the frame, the magnet goes in the door. Both halves have to be present for the contact to work, so confirm you're getting a complete set for each opening rather than sensor bodies alone.

On any opening where the frame and the door edge can both take a 1 inch recessed bore, yes, and the SPDT contact set means it will interface with whatever panel logic each door uses. Where you can't drill, or the location is classified hazardous, you'd substitute a surface mount contact or an ACSI pneumatic model from the same 1335 family respectively.

The ACSI 1335 Series is commercial access control hardware, not a residential burglar alarm contact. It's specified on institutional and commercial openings where a controller, annunciator or access control panel needs a confirmed door position signal, typically alongside an electric strike or maglock.