Lot 1920s radio technology books w/illustrations National Radio Institute

Lot of six old 1920s vintage technical books from the early days of radio. These were published by the National Radio Institute as part of their - Complete Course in Practical Radio -. They are in nice vintage condition with minor wear.

There are:

Radio Inventions - copyright 1926 with 46 pages including photos and illustrations. This is marked on the cover as being part 1 of 2 (but the second part is also bound into this volume).

Radio Service and Repairs - copyright 1926 with 28 pages including photos and illustrations;

Definition of Radio Terms and Symbols - copyright 1926 with 28 pages. This has some pencil markings;

Radio Diagrams and Draftsmanship - 21 pages including technical symbols, schematics etc.;

Radio Retailing and Salesmanship - copyright 1926 with 28 pages including photos and illustrations;

Radio in the Farming Community- copyright 1926 with 15 pages including photos and illustrations;