Abstract: Magnetization inversion data at different frequencies are recorded as part of servo information before and after an erasing gap between a data sector and a servo sector, the time interval between pulses read out from these magnetization inversion data is detected using a gap detection timer, and a timing for reading out servo information is obtained according to the result of detection by the gap detection timer.

Abstract: A velocity control unit of a detecting head consists of a differentiation circuit for differentiating a reference velocity signal and feeding it via an analog switch to a first-order lag circuit which generates a feedforward signal. The analog switch is controlled by a constant velocity/deceleration detecting circuit so that it may be turned on in the constant velocity/deceleration period of the head.

Abstract: A detector for the moving velocity of a magnetic head of a magnetic disc memory device by electrically processing a position signal of the magnetic head, which includes a circuit for differentiating the position signal, means for rectifying the differentiating circuit, a circuit for sampling-hold of the rectified signal, a phase-shifter for delaying the position signal and means for generating a timing pulse signal to determine the timing for sampling, with the phase delaying characteristic of the transfer function of the differentiating circuit and the phase-shifting circuit being substantially coincided.

Abstract: A gas discharge display panel is disclosed for displaying images by selectively making luminescent cross points of main electrodes arranged to form the matrix through a discharge gap. The display includes a switching operation part which comprises auxiliary electrodes which are arranged in parallel to the main electrodes and to which a turn-on or turn-off pulse is applied and switching electrodes which cross the auxiliary electrodes to form the matrix through the discharge gap so as to select predetermined cross points of the auxiliary electrodes. The switching operation part is incorporated in the panel together with a display part comprising the main electrodes to form the matrix through the discharge gaps whereby switching circuits for switching each of the main electrodes which are complicated and expensive can be improved.