This book contains more than 400 simple electronic circuits which are developed and tested in practice by the authors. The technical solutions presented in the book are intended to stimulate the creative imagination of readers and broaden their area of thought. This should allow readers to look beyond the horizons of possibilities and use ordinary electronic items in a new way. This book includes new and original radio electronic multipurpose circuits. The chapters of the book are devoted to power electronics and measuring equipment and contain numerous original circuits of generators, amplifiers, filters, electronic switches based on thyristors and CMOS switch elements. Wired and wireless systems as well as security and safety systems are presented. Due to the high relevance and increased interest of readers in little-known or not readily available information, the different chapters of this book describe the use of electronic devices in industrial electronics and for research, as well as new instruments and equipment for medical use, gas-discharge and Kirlian photography. A number of technical devices presented in this book are related to research of the mysteries of the earth, nature and human beings by using radio electronic devices. This book will be useful for both radio amateurs and professionals.