Folks often ask me if there are digitized versions of switching manuals and schoolbooks available. There are many and they can be found at various places around the Internet, including TCI and The Internet Archive. Sometimes it can be hard to navigate those sites if you're not 100% sure what you're looking for, so I've compiled a list below. This list is by no means complete. It should be enough to get you started.
Many of the digitized documents were scanned and compiled by me, or Astrid Smith, and are the result of thousands of hours of work (we've scanned and processed perhaps 20,000 pages between us). If you'd like to say thank you, you can make a donation to the museum.
The introductory texts are meant for people who required familiarity with switching systems, but were not necessarily going to be working in a switchroom. Therefore, they tend to me much more generalized, and much less focused on actual circuit operation. They are a good start for someone who does not require in-depth technical training.
The school books (as they are known to us) are the educational materials that craftspeople studied while preparing to work in a switchroom. They are "introductory" material, but are still often too dry and detailed for beginners. If you've don't have a large telephone switch in your home lab, I suggest starting with "Introductory Texts" above.
The general texts provide a good overview of concepts related to switching, while not diving too deep into any particular system. This is by no means a comprehensive list. It's just what I happen to have available right now.