| 摘要 |
An apparatus and method for reading punched cards having data columns parallel to one edge of the card with each data column containing a coded pattern of punches wherein the card is moved past an aligned array of sensors that are mounted to be in alignment with each data column of the passing card. The invention provides for synchronously supplying a parallel digital signal that accurately represents the characters encoded in each data column even though the aligned sensor array is not maintained in precise alignment with the passing data columns and/or the card is not moved past the array at a uniform rate. The synchronous reading is accomplished by sequentially performing two detection sequences to detect two conditions that occur as the card and encoded data columns move by the sensors. The first detection sequence constitutes a determination that at least one unpunched card region has passed by each sensor since the start of the first detection sequence. In effect, the first detection sequence detects the passage of an unpunched region separating adjacent data columns even though the moving data column and sensor array are misaligned with one another to the extent that various sensors are exposed to a punched data location at each moment of time. The second detection sequence is automatically initiated following the first detection sequence and constitutes a determination that one data punch has completely passed by a sensor to effectively determine that an encoded data column is just then moving beyond the sensor array. The sensor signals immediately prior to the detection of this condition constitute, and are supplied as, a digital signal representing the character encoded in the passing data column. Since the first and second detection sequences are sequentially performed in accordance with the pattern of punches in the encoded data columns, synchronous card reading is effected to read each character encoded on the card. |
