Addiator

The Addiator is a mechanical add/subtract calculator, once made by , Berlin. Variants of it were manufactured from 1920 until 1982. It is composed of sheet-metal sliders inside a metal envelope, manipulated by a stylus, with an innovative carry mechanism, doing subtract ten, carry one with a simple stylus movement. Some types of Addiators can also handle negative numbers (with a complementary bottom window or by providing a subtraction mode on the back side of the device). More expensive versions have a built-in slide rule on the back.

Addiator

The Addiator is a mechanical add/subtract calculator, once made by , Berlin. Variants of it were manufactured from 1920 until 1982. It is composed of sheet-metal sliders inside a metal envelope, manipulated by a stylus, with an innovative carry mechanism, doing subtract ten, carry one with a simple stylus movement. Some types of Addiators can also handle negative numbers (with a complementary bottom window or by providing a subtraction mode on the back side of the device). More expensive versions have a built-in slide rule on the back.