Klaus Jürgen Thiesler’s ‘2-Wire Interface’ was published in Elektor magazine in the form of both basic and low-current versions. Each variant used two transistors and a handful of other components to hook up an LED and a pushbutton to a microcontroller. The author still felt driven to simplify this arrangement further and can now provide a solution that, with only two resistors and a single I/O pin, could hardly be minimalized any more.