Medium: “…When readers need access to a book that is essentially “locked up” in print, help is starting to be on the way through the concept of Controlled Digital Lending. This is an approach to library curation that allows print books to be digitally loaned in an environment that restricted people’s abilities to redistribute or copy the book while providing digital access on e-readers, computers, or even phones. Controlled Digital Lending (CDL) was started so that readers could access books that are out of print or difficult to find but are still in copyright. CDL functions similarly to how a library lends out physical materials. This means that libraries have complete control over the number of copies of each book that is circulating.
CDL works when a library scans a digital copy of a book they already own or accesses a scanned copy through a repository like the Internet Archive. It is then loaned out to patrons or other libraries. When the electronic version is “checked out”, the physical copy of the book becomes unavailable and vice versa (even at the Internet Archive’s vast storage site). This ensures that only one copy, the one purchased copy, is being loaned at one time. These digital copies of books have locks placed on them that allow the reader to access the book for a certain period of time. Once the library loan period expires, the book file automatically expires and is “returned” to the library, making it no longer accessible to the person that requested it..”