| 摘要 |
Apparatus for reading punched cards is equipped with a punch mechanism for punching a hole at a specified area of a card to indicate implementation of the instructions stored on the card and read by the apparatus. The apparatus also has a sensing mechanism acting at the specified area of the card to check whether a hole already exists there when the card is inserted in the apparatus. The sensing of the presence of such a hole, indicating that the instructions on the card have already been implemented, prevents a repeated implementation of the instructions. Upon a card, not having a hole in the specified area, being accepted in the apparatus for reading of the instructions therefrom, the punch mechanism is locked against operation until a signal indicating implementation of the instructions is received. The apparatus finds particular application in process control.
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