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 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.