| 摘要 |
The optical reader of the invention uses a discrete number of pulses to time the passage of each column position, samples hole data at four selected count positions and interrogates the samples to ascertain whether the condition of the samples indicates the presence or absence of data or an error condition. When valid data is sensed by data indications adjacent one end of the sample sequence, the interpreting circuit also indicates whether the presence of the hole occurred early or late with respect to nominal timing. In addition mark read data may be read at the same read station using selected samples that are interpreted as presence or absence of data or an error condition using the same interpreting circuitry.
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