Magnetic data storage devices

Claim 1

APPARATUS FOR RECORDING A PREDETERMINED NUMBER OF SYNCRONISING SIGNALS ON A TRACK OF ROTOR MAGNETIC STORAGE DEVICE COMPRISING A DISC MOUNTED FOR ROTATION IN SYNCHRONISM WITH THE STORAGE DEVICE; A SERIES OF SENSIBLE INDICIA EQUAL IN NUMBER TO SAID PREDETERMINED NUMBER OF SYNCHRONISING SIGNALS AND SPACED AT SUBSTANTIALLY UNIFORM INTERVALS AROUND A CIRCULAR TRACK OF THE DISC; SENSING MEANS RESPONSIVE TO THE PASSAGE OF SAID INDICIA PAST THE SENSING MEANS DURING A REVOLUTION OF THE STORAGE DEVICE TO PRODUCE A TRAIN OF FIRST SIGNALS EQUAL IN NUMBER TO SAID PREDETERMINED NUMBER; A FIRST TRACK OF SAID STORAGE DEVICE; FIRST RECORDING MEANS RESPONSIVE TO SAID FIRST SIGNALS TO RECORD SAID FIRST SIGNALS AT SUBSTANTIALLY EQUAL SPACING IN SAID FIRST TRACK; DRIVING MEANS OPERABLE TO ROTATE THE STORAGE DEVICE AT A CONSTANT INVARIABLE SPEED; READING MEANS OPERATIVE, DURING ROTATION OF THE STORAGE DEVICE AT SAID CONSTANT SPEED, IN RESPONSE TO SAID RECORDED FIRST SIGNALS TO GENERATE A TRAIN OF SECOND SIGNALS AT A SUBSTANTIALLY CONSTANT FREQUENCY AND EQUAL IN NUMBER TO SAID PREDETERMINED NUMBER; A SECOND TRACK ON SAID STORAGE DEVICE; SECOND RECORDING MEANS OPERATIVELY COUPLED TO SAID SECOND TRACK; CIRCUIT MEANS INCLUDING A FILTER NETWORK OPERATIVE TO ATTENUATE, RELATIVE TO SIGNALS OF SAID CONSTANT FREQUENCY, ALL OTHER SIGNALS, AND HAVING AN INPUT CIRCUIT CONNECTED TO SAID READING MEANS AND AN OUTPUT CIRCUIT CONNECTED TO SAID SECOND RECORDING MEANS.