A lot of schools have started using the computers and the tablet PCs for classes nowadays but still the blackboard is used for most classes.
When students or teachers wipe everything clean on the blackboard for the next class, it wouldn't be clean as supposed to be if wiped by the eraser with full of powder of chokes on, would it? For avoiding that, there is an eraser cleaner in a classroom.
The eraser cleaner looks just like a box. You only put an eraser on the cleaner and turn the switch on. Then cleaner sucks the powder choke with the vacuum sound.
I feel happy somehow about the fact that even though with the high technology, young generations use the same thing which I used ages ago in school.