I mounted the sensor high so it will be out of the way of things to prevent it from getting knocked around and tearing wires or bumped out of alignment, but it's still in contact with magnet when fully closed . Not sure of the exact type of sensor (Threw paperwork away), buts it's what the guys at Smarthome sent with the kit (Pretty rugged, metal construction). I have it set-up so the the LED on the keypad is illuminated (on) when the door is open and that's what I want it to display. I guess if I have to choose which condition I want a higher level of confidence as to whether the door is open or closed that would be CLOSED.