MARK Sensing, a feature of the Electric Card Reproducing Punch, operates on the principle that graphite conducts electricity and thus can actuate punching mechanisms. It converts data in the form of a graphite deposit in the marking column of an accounting machine card to a hole made in the desired punching column.

The marking area of a card designed for mark sensing is laid out in conventional fields and columns three times as wide as those used in regular punching. Thus, for mark sensing, only 27 columns are provided.

A Mark Sensing Device has a capacity of ten columns of mark sensed punching. When more than ten mark-sensed columns must be punched, additional runs can be made or one or two more devices can be installed to increase the capacity to twenty or to twenty-seven columns, respectively. Thus 27 columns of mark sensing can be accommodated on each side of the card.

Only one digit (0-9) should be marked in any single column. However, marks may be made in the eleventh or twelfth positions in any column, irrespective of a mark for any regular digit (0-9) in that column.

As an integral part of the Mark Sensing Device, 10 positions of double punch and blank column detection are provided to check the punching. The purpose of this feature is to verify that all the desired columns are marked correctly as to completeness and accuracy.

Accounting machine cards correctly marked can be punched at the rate of 100 per minute regardless of the number of columns punched.