Abstract: A data processing system which synchronizes an internal clock with an external clock. The system can be incorporated as part of a magnetic reproducer apparatus or magnetic recorder apparatus. The recorder/reproducer apparatus utilizes ratio encoding schemes to convert conventional data into encoded data to be recorded onto a magnetic medium. It can also read the encoded data from a magnetic medium and convert it back into conventional data. In either case, the synchronized internal clock is utilized as the time base for the ratio encoding.

Abstract: A magnetic storage disc for storing information comprises a spiral of magnetic tape supported edgewise on a disc having a flat bottom surface, one or both sides of the magnetic tape being available for recording information thereon.

Abstract: A motor speed control arrangement in which the back EMF of the motor is sensed in all operating modes and is used as a measure of the motor speed. The effect of commutator ripple due to varying rotor resistance is compensated by adjustment of resistors associated with an operational amplifier, so that the output of the amplifier provides the average value of the back EMF without distortion. A comparator compares the output of the amplifier with an input reference signal denoting the desired speed of the motor and applies an error signal to a driving circuit which drives the motor with current in a manner that tends the error signal to attain minimum or zero value.

Abstract: A continuous loop tape cassette with a rotating tape coil carried by a flanged, reverse e-shaped hub in fixed radial angular relation to the base of the cassette. A tape receiving arc portion of the hub has a radius sufficiently great relative to the spring modulus of the tape to prevent binding. The arc portion is undercut to contain the tape.