Abstract: A magnetic recording and reproducing circuit comprises a recording and reproducing head including a recording coil; an erasing head disposed upstream of the recording and reproducing head and including an erasing coil; a flip-flop which receives pulse-shaped record data and outputs an output signal which reverses the state in accordance with the pulses of the recording data; a delay circuit which receives the output of the flip-flop and delays such output by a predetermined period of time; a record driver which receives the output of the delay circuit for causing a recording current to flow through the recording coil of the recording and reproducing head; and an erasing circuit for causing an erasing current to flow through the erasing coil of the erasing head at the time of recording.

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: In order to reduce the interference of readout signal waves that increases with the recording density in a magnetic disk device, the readout circuit is provided with a waveform equalizing circuit consisting of a resistance circuit, a delay line, and a differential amplifier to produce a signal advanced by a certain time and attenuated by a certain degree and a signal delayed by a certain time and attenuated by a certain degree. These signals are subtracted from the original signal to decrease the half-value width of the readout signal, thus reducing the interference between the waves. However, these conventional attenuation factors of the advanced and delayed signals cannot be changed freely so that the half-value width of a readout signal cannot fully be decreased without increasing the undershoot in the head or tail portion.