Abstract: In a magnetic recording system, an asymmetry detector reverses the phase of a read, single-frequency test signal to indicate to a micro-controller whether recording signal asymmetry is present. Upon detecting such asymmetry, the micro-controller causes a current source coupled to the recording head to adjust a write current to correct the timing of a written data signal.

Abstract: In a magnetic recording system, a loop-back test circuit provides a technique to test a magnetic recording head, a read circuit, and a write circuit to a read-write head, is sensed through the voltage generated at the head by the test current, such that a small voltage portion of the test signal is transferred through a resistor toga read circuit. The voltage portion is then filtered through a capacitor to form detectable peaks such that the read signal is generated with pulses corresponding to the peaks.

Abstract: A method for duplicating data on a rotating magnetic disk in sectors on concentric tracks so that the sectors are aligned with each other from track to track and referenced to an index mark. The index mark is sensed as the disk rotates. The time elapsed between sensed index marks is counted to define the angular displacement of the disk. A magnetic head is moved successively to the tracks on the disk. Data to be duplicated is recorded in sequence, sector by sector, on the respective tracks beginning at different offsets from the index mark such that recording begins with the next sector encountered after the head arrives at the respective tracks.