Abstract: A system of detecting position drift in the motor due to lost pulses. Due to imperfections in the motor, the timing of the commutation pulses is not uniform but forms a unique repeatable signature. The system identifies lost pulses by using a pattern recognition technique on the signature of the motor commutation pulse rate. By detecting when a pulse is lost, the system can apply a correction to the pulse count. Accordingly, the real time correction of the pulse count allows for the system to operate with significantly reduced mispositioning errors. In addition, the system requires far fewer calibrations.

Abstract: An apparatus for determining angular positions of DC motor includes a capacitor connected in parallel with the DC motor. The current flowing through the capacitor, at any given time, is an AC ripple current responsive to a commutation event of the DC motor. The capacitor partially sources the motor current ripples during commutation and recharges itself during the off-commutation period. Since the number of commutation events per mechanical revolution is pre-determined once the DC motor is designed, the frequency of the AC ripple currents through the capacitor corresponds to the frequency of commutation, and thus a motor position of the DC motor.

Abstract: A method and apparatus are provided for dynamically switching between fonts or groups of fonts in an automatic optical character reader. A switch character which is included between a first and second group of characters triggers the selection of the appropriate memory for the succeeding font.

Abstract: Voltage regulator having current limiting circuitry. The voltage regulator includes an operational amplifier which has a substantially high output impedance and is disposed in a negative feedback configuration to provide an output signal which is the difference between a reference voltage input and the magnitude of the output voltage of the voltage regulator. Overcurrent detection circuitry is connected to the output of the operational amplifier and provides an on or off signal whenever the magnitude of the current drawn by a load exceeds a predetermined magnitude. When the magnitude of the load current exceeds a predetermined magnitude, the output of the overcurrent detection circuitry will be a low level signal which clamps or draws down the magnitude of the output voltage of the operational amplifier towards ground potential.

Abstract: A high-speed apparatus that processes a stack of documents such as bank checks. The apparatus includes a feeder for serially feeding the documents, an error-indicating character reader for reading characters on the documents, an operator's console for manually inputting characters rejected by the character reader, and a sorter for sorting the documents into groups. The error-indicating character reader includes a character reader, a printer located a fixed distance from the character reader and an AC synchronous motor that drives each document serially past the reader and printer in a continuous motion. The character reader provides a first electrical signal when it cannot read a character. A motor velocity detecting means provides a second electrical signal representative of the motor velocity.