With integrated coil surrounding Hall sensing element, A1160 functions as typical unipolar switch during normal operation: output turns on in presence of south-pole magnetic field and off when field is removed. Diagnostics mode lets current pass through integrated coils, generating ~20 G of magnetic field. Proximity of coils to Hall sensing element lets element sense field generated by coil while ignoring external fields. This feature ensures proper sensing of magnetic signal.
This story is related to the following:Hall-Effect Switches