The circular switch was designed by Konstantin Grcic and manufactured by Merten. It won the iF product design 2008 and the Design plus 2008 awards. There is the quote about functions indication of this switch and its family from the brochure of Merten product -  A “round” break out of the “rectangular” system allows shape to indicate functions: Switching = round, socket – outlets and other functions = rectangular. Allocating the round shape to the switching function creates a formal unit that we intuitively find suitable.