Setting the Default Source
The default source indicates which source (or "media set") your book is saved with.
The default source is stored as a book property, TBC_defaultMediaSource. It is used to check if a source change is required when your book opens. When a user opens your application, TB Connection will compare the current source to the default source. Unless you've set Media Connection to always populate media on startup, TB Connection will load media on startup only if the current source and default source differ.
To select a default source, simply click on one from the list of defined sources.