How does the door/window sensor work? I will place a small magnet in the door/window (has to be painted again, so it doesn't matter) and a hall sensor in the frame of the door/window.

Today I got my hall sensors from Farnell. Yesterday I was in a hurry and just ordered a few hall sensors (in TO92 housing). What can go wrong? Well, the hall sensor I ordered can not be used as a door/window sensor. The sensor I ordered is bipolar. The output is set when a S field is applied and reset when a N field is applied. The state of the output is maintained when there is no magnetic field present. I need a sensor that has an active output when a magnetic field is present (so a S or N magnetic field when the door/windows is closed) and the output is not active when no field is present(door/window is open). This means I need an omnipolar hall sensor for the door and window sensors. The output becomes active (this means low because of the open colector output) when a magnetic field is present. On monday I will receive the omnipolar sensors....To be continued.