We have been living in the electronic age for well over a century now, since the invention of the triode by Lee de Forest in 1907. Roughly speaking, in the first half of this period electronics was based solely on electron tubes, and in the second half almost entirely on silicon semiconductors in discrete or integrated form. In a relatively short transition period, electronic equipment was designed and built with neither tubes nor silicon semiconductors, but instead with selenium rectifiers and germanium diodes and transistors. Let’s have a closer look at these components.