PURPOSE: To always rapidly generate deceleration signals or acceleration signals by generating wheel comparison speed and by always evaluating the difference between the wheel comparison sped and the wheel speed.

CONSTITUTION: When a control signal ±b is set, if the difference between a wheel comparison speed VDiff and a wheel speed VRad exceeds a predetermined difference Δ (target difference) or reduced in the case of excess, the correction value is set large and never falls short of the predetermined minimal value. Since the difference is limited, a disappeared delay which can be set is generated for the purpose of making the control signals act during a minimum time and permitting slight variations of measured wheel speed without resetting (hysteresis) the control signals. The control signal ±b is set or reset.