DATA RETRIEVAL AND ERROR DETECTION METHOD AND APPARATUS DESIGNED FOR USE IN A WIDTH-MODULATED BAR-CODE SCANNING RATUS

摘要

Sudden changes in the rate at which a bar code is manually scanned are detected by circuitry which compares the time required to scan adjoining fixed-width characters of the bar code. This circuitry sums the time required to scan each individual bar and space element of every character in the bar code. The circuitry thereby generates a series of numbers proportional to the widths of the characters which comprise the bar code. Adjacent numbers in this series are then compared to determine if there has been a sudden, unacceptable change in the speed at which the bar code is scanned. If adjacent numbers differ in size by an unacceptable amount, an error indication is given out.