Means and method for dynamically tracking

Dynamic search device using an error flag signal and its method of implementation, which can perform normal track following by correcting the position of a head. The device includes a multiplexer (70) which selects an error flag signal by a mode selection signal, a system controller (80) for delivering a control signal as a function of a reference value, and a head position excitation section (90) which delivers an excitation signal to the head to set its position.