Forward and reverse sensor. The forward and reverse speed sensor is detected by the Hall principle.  Just fix two corresponding magnets on the shaft and wheel (the two magnets are symmetrically distributed, and one magnet must be installed with the N pole facing the sensor and the other magnet with the S pole facing the sensor), and fix the arrow on the detection surface of the sensor probe facing the arc of the magnet rotation. When the wheel or shaft rotates, the magnet sweeps across the sensor probe in the direction of the arrow, and line 2 (blue line) outputs a forward signal (low level), and line 4 (white line) outputs a forward speed pulse signal; conversely, line 2 (blue line) outputs a reverse signal (high level), and line 4 (white line) outputs a reverse speed pulse signal.