Disadvantage: I built this detector in the ceiling of a stairwell, so face parallel to the ground
The speed of motion detection threshold (0.6 to 1.5 m / s) is not suitable in the upward movement (climbing stairs) when the detection distance is greater than 5 m
I was forced to place a second detector in parallel therewith at the bottom level of the staircase
At the top level of the triggering staircase is satisfactory since all access doors to the stairs (distances less than 4m)