INTRODUCTION The circuits contained in this book have been carefully chosen from the great variety which have been used for different purposes. All freak diagrams and those which are unnecessarily complicated have been eliminated. No attempt has been made to include every known circuit. So many audion hook-ups, for example, contain entirely too many unnecessary instruments. The diagrams given here are the most practical and the most satisfactory known. This elimination of non-essentials is a part of the policy which has been followed thruout the Radio Department of Everyday Engineering, a policy which has won universal approval among the radio experimenters. Circuits developed subsequent to the publication of this book will be found in the current issues of Everyday. May, 1922. Digitized by Google., Blank pages for "Additional circuits" (68-72)