Xerox Xrx-230 Calculator «SECURE METHOD»

Disaster struck at 3:00 AM. A blown fuse plunged the floor into darkness. Arthur froze, his finger hovering over the decimal point. If the machine didn't have a reliable memory circuit, hours of work could be lost. He waited, heart hammering against his ribs, until the backup generator kicked in with a groan. The green display of the XRX-230 flickered, stabilized, and—to Arthur's immense relief—held the current figure.

It used a standard two-color (black and red) ribbon. Positive numbers were printed in black, while credits and negative balances were struck in red—literally keeping the user from being "in the red." xerox xrx-230 calculator