Here's the AKAT-1 from Poland, "the first transistor-based differential equation analyzer, from 1959."
AKAT-1 is an analog computer. Back in the 1960s, this approach offered speed and acceptable accuracy without the complexity of digital logic. The result was a device that could solve relatively complex differential equations in real time, as long as you weren't after precise values. Alas, time has passed it by and it now leads a life of leisure at the Museum of Technology (Muzeum Techniki) in Warsaw, Poland.