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Arithmometer VK-1
The VK-1 mechanical key-driven calculator was developed to mechanise calculations embracing the four arithmetic operations, primarily multiplication and division. VK-1 is a computing machine requiring the input data for each operation to be entered manually using the keyboard (lever).

VK-1 is an improved version of the Odhner Arithmometer. The slides here are replaced with a 10-digit keyboard (1) used to enter the numbers. On the right-hand side, there is a key (2) designed to move the carriage into the left-hand position (used to divide the number after it was entered on the keyboard). The lever (3) serves to reset the entered numbers. The handle (4) is used for the same purposes as in the arithmometer. The red signal window (5) shows the direction of the revolution counter. Lever (6) serves to reset the revolution counter. (7) and (8) stand for the revolution and result counter windows respectively. There is also a monitoring window (9). Lever (10) serves to reset the result counter. On the left-hand side of the keyboard, there are keys [<-] (11) and [->] (12), which are used to move the carriage one position left or right.

The use of keyboard input boosted VK-1’s capacity by approximately three times as compared to Felix arithmometer. Скорость работы на ВК-1 составляла: 900–1000 сложений в час, 310–330 умножений, 190–210 делений в час.

VK-1 was the second most widespread arithmometer in the USSR after Felix-M.

The calculator was produced at Schetmash in Penza. Start of serial production — 1951. Sale price — RUB 750. Weight — 6 kg. Size — 310✕200✕160 mm.