Kalmár’s logical machine

Kalmár’s logical machine

Professor Kalmár, with his co-workers started to build an electronic computer in the mid-1950s, but in the end instead of finishing it - continuing the example of the Ferranti logical machine - he created a logical machine with completely original design.

The machine consists of six operational boxes, each of them is realising basic operations with two variables, 39 these being the so-called logical gates, so by using them optional logical functions can be created. The important innovation is that the boxes represent the “true” (T) or “false” (F) value of the logical variables not with voltage levels, but with short circuits physical connections.

As a result, the input points are realised with three connecting sleeves instead of two, and the middle sleeve is in short circuit with one or another on the side depending on whether the input variable has T or F value. The same thing is valid for the output function values, that naturally depend on the elementary function “wired” into the box for what answers they give to the input variable combination.

The logical machine can handle 8 input variables, and with the triple wired connection in the sufficient order of the right number and type of boxes optional logical function can be created, whose truth table we can also create if we record the corresponding input and output values.

The input variable combinations can be automatically generated with the help of the marker machines used in the telephone exchanges, for example with 3 marker machines all the possible combinations of 8 or 9 input variables can be realised (256, or 512 possibilities).

Although the logical machine was built for educational purposes, it was theoretically suitable for the examination of telephone exchanges and railway security systems as well.

Kalmár's logical machine, as the first messenger of the Hungarian information technology, was made in 1957, and - together with the Ladybird of Szeged - was introduced with great success in 1960 at the Budapest Industrial Expo.