ld's favorite English course. Interchange is a four-level, American English course that has been used by over 50 million students worldwide. This Level 1 Full Contact has 16 units and includes the Student's Book, Workbook, video activity sheets. Inside each book is a single-use code for the Digital Pack to access the Digital Workbook with hundreds of self-graded exercises, audio, videos, and an eBook, all available on the Cambridge One platform. The Digital Pack is mobile-friendly and can be used on a smartphone, tablet, or computer.