Titles in the Ebook Central catalog are available in one or more “Access Models.” The access model determines how the book is available to patrons. The pricing of each access model is set by publishers. The library can set download lengths for each model and loan lengths for Non-Linear titles to ensure maximum patron access.
 
Non-Linear (NL) access model
Under this model, titles are not restricted to linear distribution - one patron at a time - but rather they can be lent to any number of patrons concurrently. The number of days used for each loan instance is subtracted from the total number of annual loan days set for the title - usually 325. (See loan trigger events). For example, if four patrons each trigger a ten day loan for the same title, 40 days are deducted from the title's 325 loan days. This will display as 285/325 and you have 285 total loan days left. The combined number of loan days cannot exceed the annual loan days in a year. Loan days renew on the anniversary of purchase, at no additional cost. The library is able to control patron access to titles with expired loan days. Automatic email alerts can be configured to notify the library when a Non-Linear title has a limited number of loan days are remaining.
 
1-user (1U) access model
One person can access the ebook at a time. Librarians are provided with options such as reserving an online access by setting download days to zero for individual 1-user titles that are in high demand. Chapter Download is always available, even if Full Download has been disabled.
 
3-user (3U) access model
The 3-user access model restricts access to three concurrent users. A user is a patron accessing the title in the Online Reader or with an active download of the title. Access to 3-user titles can be managed by preserving Online Reader access for one, two or all users. If a library owns multiple copies of a 3-user title, the number concurrent users is multiplied accordingly. For example, if the library owns two copies of a 3-user title, six patrons can access the title concurrently.
 
Unlimited (UA) access model
This access model allows titles to be available on an unlimited access basis. Any number of patrons can access Unlimited titles concurrently for any number of days per year, according to the download options set by the library.