Bipolar Hall switches need to use N and S poles to control high and low levels respectively, so as to output signals. Generally, the N pole responds to high and the S pole responds to low. For example, when the S pole is close, the output is low, and when the N pole is close, the output is high.
There is a special form of bipolar Hall switch called latching Hall switch, which is turned on when the S pole is close, and remains on when the magnetic field leaves; it will be closed when it is close to the N pole, and will remain closed after the magnetic field is removed until the next time the magnetic field changes. This characteristic of maintaining the last state is called latching characteristic, and this type of Hall element is a bipolar latching Hall element.