This book was originally published in 1980. Owing to the increasing use of electronic instrumentation in medical practice it was desirable that medical and nursing personnel have some technical knowledge of electronic equipment. It was the aim of this volume to help those members of the medical profession to develop this knowledge. The reader will find a survey of basic principles and methods, with illustrations of the applications in the most common fields of medical practice, for instance the registration of cardiac activity by means of the ECG. More complicated instrumental systems, such as those used for intensive care, are discussed in the light of the basic principles. These include acquaintance with three important concept in electricity: voltage, current and resistance.