An annular magnetic encoder capable of detecting an absolute position precisely by specifying the shape of a magnetization pattern. The delay cells are operable to receive respective differential inputs and to generate inverted outputs. The measuring cell is provided with an inlet on the side opposite the window. As the door moves towards the wall to its fully open position, it rides over the ramped surface and is latched open between the release lever and the mounting bracket. The fork clamp includes a horizontal mounting surface that is formed to offset the fork’s rake angle to cause the horizontal mounting surface to rest in a substantially horizontal alignment with respect to a ground surface.