One of the most important innovations in “Piazza virtuale” was the idea of controlling programme elements with the help of the telephone keyboard. This was made possible by the introduction of touch-tone or multi-frequency dialling in analogue telephony in Germany at the beginning of the 1990s. With multi-frequency dialling, the keystroke signals of a telephone are converted into audio frequencies that can be further processed by computers. The idea came to Benjamin Heidersberger as early as 1990, as these excerpts from his sketchbook show. The process was later used in other television shows.