At my library the only way for the public to get in or out is through our security gates. To put it simply, if you have a library item that hasn't been checked out properly, which is a simple process that turns the library item's security off, and you walk through our gate, a loud, high pitched, screeching alarm will sound.
I probably don't have a great many blog posts about our security gates because it is not a high interest area of my library. But I did realize today that with this one simple, albeit insanely loud alarm, the entire story of all transgressions is told in the number of times the alarm goes off.
This means that someone is stealing something.
This is expressed in a person setting off the alarm and continuing on their way.
This means that an error was made and an item was not checked out or desensitized for the alarm system.
It is expressed in the alarm going off and then the patron hearing the alarm and returning to the library thus setting off the alarm the second time
Three or more alarms:
This means that we have a hopelessly confused person on our hands.
This is expressed in a patron setting off an alarm. Hearing it, coming back. Trying to leave again, and then repeating the process in an endless loop until we intervene.