A second mechanism for entering numbers in a calculating machine was the pinwheel. As the name suggests, pinwheel machines had a series of wheels (initially mounted vertically) with nine retractable pins mounted around the edge. Setting a digit released a corresponding number of pins. Rotating the crank transferred the digits of the number to the mechanism of the machine. The pinwheel calculating machine was invented in the United States by Frank S. Baldwin and in Russia by the Swede W. T. Odhner. Odhner’s patents formed the basis of Swedish, German, French and later American calculating machines.
