In the first place electronic noise is a disturbing effect in communica tion systems. Investigating the noise, one has also the possibility of obtaining interesting explanations about physical phenomena. Thereby one should not forget, that a special form of noise - the BRoWNian movement - has given the final evidence for the existence of atoms, which was questionable for a long time. Using NYQUISTS theorem the noise of a system in thermodynamical equilibrium gives a useful method for the temperature measurement. Each dissipating process is correlated with a noise. Additional fluctua tions are...