Addiator

• mechanical

The Addiator is a mechanical adder produced by the Addiator Gesellschaft of Berlin from 1870 to 1982. It consists of a series of racks enclosed in a metal container and operated by a stylus. The Addiator, produced in dozens of models and millions of copies, was a great success, so much so that its name was often used as an antonomasia to indicate all rack adders.

• mechanical

The Addometer is a mechanical adder which in terms of use and external appearance resembles Blaise Pascal 's pascaline .

The adder looks like a heavy ruler, about 30 cm long. Circular slots allow you to operate numbered wheels placed inside, through special holes made on the wheel. Each hole corresponded to a number written in large characters on the inside of the slot and its complement to 9, written on the outside in smaller characters. To add, the tip of the stylus was placed in correspondence with the large numberand the disc was rotated clockwise. To subtract, on the other hand, the stylus was placed in correspondence with the external number and performed a counter-clockwise rotation. A much simplified mechanism compared to that of Pascalina allowed the carry over of the tens. The result appeared automatically and it was possible to reset it by pulling the tab on the right of the instrument. 

It was produced from 1928 until the 1960s by Reliable Typewriter and Adding Machine Co .. The numbers were imprinted on perforated and toothed discs. These were very cheap and reliable instruments, so much so that they were covered by a one-year warranty, which was quite unusual for the time.