A passive all fiber optic encoder that will be able to determine speed, position, and direction of movement of a movable object. Additionally, the invention provides use of said salt adducts for the preparation of medicaments for the improvement of cognitive functions in a healthy subject. The purpose of the intermediate seal is to confine the working fluids, being acted upon by the reciprocating motion of the engine piston, across the stationary interface of the engine cylinder and rotative surface of the disc valve. In an embodiment, two phase steps, having opposite polarities, are successively introduced into the PLL, and the time-to-crossing measurements resulting from these two phase steps may be averaged, and this average is used to determine a loop parameter.