Briefly, in an accessible form and at the same time, the main theoretical provisions on the analytical representation of deterministic and random signals, their conversion into linear and nonlinear devices, detection, optimal filtering of signals, and evaluation of their parameters are quite strictly stated. One of the sections of the book is devoted to the basics of information theory. Almost all theoretical provisions are illustrated by relatively simple examples. The presented material is intended primarily for students and graduate students studying in optical-electronic and radio engineering specialties.