A method and apparatus for operating a security gate, is disclosed which may comprise a driving member connected to the security gate and adapted to move the security gate from a first position to a second position, responsive to operation of the driving mechanism; a position detection device associated with the operating mechanism and adapted to determine a first distance of the driving mechanism from a first reference point and a second distance of the driving mechanism from a second reference point, and to determine the position of the security gate based upon the relation between the first distance and the second distance. The apparatus and method may have the first reference point being the position of the position detector and the second reference point being at a preselected distance from the position detector. The apparatus and method, further, may have the position detector be an ultrasound, radio frequency or light wave, or the like, transmitter/receiver, and the first distance may be is measured by reflecting waves from a moving target moving as does the driving member and the second distance is measured by reflecting waves from a fixed target fixed in relationship to the transmitter/receiver.