This device is a magnetic field sensor switch based on the principles of hall effect. Its open-collector output is in the high-impedance state in the absence of a magnetic field; When brought close to a magnetic field, its output goes LOW. When the magnetic field is removed, the output returns back to high-impedance state. This device is useful in projects such as Brushless Electric Motors, Electric Motor Speed control, Contact-less Revolution counters, POV (Persistence of Vision) Based LED Displays etc.

*Please note that the output of this device is an open-collector output which has two logic states of High-impedance and LOW. Connect a resistor of 1kΩ between its output and Vcc to get digital logic states of HIGH and LOW. Consult the datasheet for further information.