Over 900 color figures are used. 
Color adds a dimension to figures that improves comprehension.
For instructional use, I have prepared color editions of
Klystrons, Traveling Wave Tubes, Magnetrons,
 Crossed-Field Amplifiers and Gyrotrons
Klystrons, Traveling Wave Tubes, Magnetrons,
 Crossed-Field Amplifiers and Gyrotrons
Color Edition

For use in class rooms, a 3-ring notebook format is used because the 
pages lay flat on the table.
Because of the large size, the latest version has been divided into two volumes.