Before vacuum tubes or transistors (chips), engineers used electromechanical relays to build digital logic circuits. Using Boolean logic and relay switching, pioneers like Claude Shannon, George Stibitz, and Konrad Zuse launched the computing revolution in the late 1930’s.

Building a relay-based computer is more than a fun retro-engineering challenge. It is a hands-on masterclass  showing how the essential on/off switch underpins all forms of digital computation.

For a backgrounder, select "From Pascal to Zuse" from the main menu above. Select "R30 Computer" to get an overview of a DIY relay-based  computer. The "Table of Contents" has links to explainers covering binary math, logic, relays, several interactive demos and historical perspectives.