When taking pictures of these snazzy 24h book return terminals outside the National Library in Singapore, some lady selling t-shirts nearby noted sarcastically: “Beautiful, isn’t it?” Only slightly embarrassed, I told her that this was part of my job (cough, cough). Still amused, she was nice enough to explain to me how the system worked.
Basically, books are passed through a large rectangular slot, being identified by a barcode scanner. Once a book is identified, the customer receives two forms of feedback. One is via a text display (changing from “Ready” to “Returned” and then back again), the other is via a live video feed from inside the terminal, showing the book actually slide into the return box inside: a simple but very elegant way to give the user instant positive feedback!