A means for sensing relative position and speed of mechanically functional machine members having accessible ferromagnetic portions is described. The method is based on creating, sensing, and annihilating local transitions in the polarity of remanent magnetization in surface regions of such parts while in motion, in analogous fashion to conventional magnetic recording. The presence and location of a transition, sensible by its associated external field, constitutes stored information carried by the member. Bias and “erasure” are provided by a permanent magnet; transitions are “written” by pulsed currents through a coil on a gapped core and “read” by Hall-effect field sensors located at purposeful distances downstream. Transition position is determinable within ±0.1 mm. Velocity is determined by the elapsed time between a recording pulse and its detection. Experimental data from a polyurethane timing belt reinforced with cabled steel wires demonstrates system operation. ©1997 American Institute of Physics.