Excuse me

When I told the beep beep incident to my family I got a big booing. The reason of the boo is mostly it was not a thing that a grown-up will do. But excuse me. It was not a spur of the moment if I think back. I had been wondering how the detector worked. Everytime we borrow or return a book the clerk press its binding part(背表紙) against a machine and slide the book along it just like shop clerks do when they read a creditcard. So you would think that they are somehow recording a mark on a book perhaps electronically for the checkout. I examined the book. But it has no recording media such as IC tips or magnetic media as Passerby pointed out. I asked a librarian.
"May I ask what the machine is for?"
"Oh, it is marking the book I believe."
"So, how does it mark? I can't see any means on books."
"Your guess is as good as mine（私もわかりません）."
I suspected that she was just going through the motions(ふりしてるだけ）. The machine may work just as a detterent means like the self-defence force in Japan which looks scary but actually pretends to prepare for a "possible war". The machine was just a scarecrow or possibly they switch it off due to frequent false alarm by machine blunders.The skeptisism was born and had grown to the size that triggered the beep-beep incident. So you must understand I am not a man who act on impulse.(まず家族に分からせろって）