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Monroe 1800-Series Calculator Mark Sense Program Card
Monroe 1800-Series Mark-Sense Program Card, Circa 1974
Used in Monroe CR-2 Mark Sense Card Reader
The CR-2 Mark Sense Card Reader could be connected to any Monroe 1800-series
programmable calculator, allowing program information to be leaded from
the card into the calculator's memory simply by inserting the card into
the CR-2 reader. The CR-2 reader's motor draws the card through the
reading station automatically, with the card exiting throug the rear
of the reader. The information encoded on the card is transferred into
the calculator's memory. A total of 30 program steps can be coded onto
one of these cards, one step in each column of the card. The program
steps are encoded into 8-bits, in octal (base-8) representation. A filled-in
box (using a #2 pencil) represents a binary 1, while leaving a box unfilled
represents a binary 0. The bottom-most box in each column allows the
instruction encoded in the column to be ignored if the box is filled in,
to allow for incorrectly coded columns. The black marks near the bottom
of the card are timing marks, read by the photoelectric reading mechanism
of the card reade to generate the timing for reading the data from the card.
Each card is made of standard punch-card stock, and is printed with a
reddish-pink ink, which is invisible to the mark sensors in the reading
station of the CR-2.
Thanks for Andrew M. Andrews III for donation of a large number of these cards to the Old Calculator Web Museum