Abstract: Apparatus for producing information pulses including, for example, two magnetic pick-ups spaced apart nd, where n is any positive odd integer and d is equal to one-half the spacing between the centers of two immediately adjacent teeth of a rotatable ferromagnetic armature. The pick-ups have coils which are connected in phase so that noise is neglected. The apparatus is selective and discriminates against voltages induced by vibration, by an internal combustion engine ignition system coil or by other means. The system is useful for providing a velocity analog for any purpose including, but not limited to, an anti-skid braking arrangement for motor vehicles.