The book discusses in detail the physical nature and mathematical description of common noise sources. Noise of field and bipolar transistors and amplifying stages on them are considered. Methods of measuring low currents, voltages and charges are described, the results of the study of the work of detectors, mixers and radiation amplifiers are given. A separate chapter is devoted to the study of noise in television transmission tubes. Of great interest is the material on lighting measurements. The book is intended for scientific and engineering workers specializing in the development, manufacture or use of electronic equipment, as well as for students of radio engineering and electronic specialties of universities.