Library security system: improving the magnetic strip system

Factual Questions
1

I work in the Nashville Public Library, and I can’t help but notice how many man-hours are wasted “thunking” books after they’ve been turned in. Each book contains a strip of a specific alloy, which when exposed to the particular radio signal emitted by one fo the two security towers gives off a signal of its own. That signal is detected by the second tower, which sets off the alarm. However, if the strip has been magnetized, the second signal is not sent, and the system is not set off.

Thus, the proceedure is as follows:

A book is checked out by the patron.
The librarian runs the book over a desk-mounted magnet, magnetizing the strip and desensitizing it with regards to the security system.
The patron leaves.
Here, either the patron returns the book, or we call out our ninja death squads. For the purposes of this discussion, we’ll assume the former.
The book is checked back in by the librarian and placed on a particular book cart.
A library grunt (i.e. me) takes the books one at a time and runs them over a large (1’x1’x5") desk-mounted device that emits a brief magnetic field when something crosses its eye. It emits a thunking sound when this is done, and thus the process is called “thunking”.

OK, so far, so good. But as I say, the process is horribly inefficient. Unfortunately, I can find no way to conduct the magnetic field away from the device itself. Perhaps superconductors are in order. However, the difficulties of dealing with liquid oxygen would offset any gain in productivity, so I need another solution. :slight_smile:

First off: how does something get de-magnetized in the first place? That I just don’t get. Understanding the basic principles would certainly help.

Second: is there any way to conduct this kind of magnetic field? I tried using my slinky, but…

Third: can I simply build an entirely new device to do the same job using parts from Radio Shack for under $30?

What I’m hoping for is some sort of archway that I can simply drive the cart through. Preferably something that wouldn’t fry every computer in the room in the process. :slight_smile:

Any ideas?

2

Do you guys call your strips “tattle tape”? That’s what we called them when I worked in the library in college. I remember the “thunker”, too (Ours made more of a “clunk” sound, so we called it the “clunker”.)

You could always propose that your library use what I call the “video store” set-up. This is where you leave all the books sensitized all the time, and then you pass them around the security towers. The patron walks through and picks up his/her books on the other side. I know of one local county library system that is set up this way. No “thunking” necessary.

3

Possible, but not plausable. We’re talking about a major metropolitan library. We’d have to redo ALL the materials in the entire system. That’s probably over a million, all branches counted. Not to mention the major redesign of all twenty branches that would be required to accomidate placing the checkout desk near the doorway.

4

I think that a big mass desensitizer would create too big of a magnetic field.

I don’t think you’re proposing something that could be made out of spare parts from Radio Shack. Sounds to me like you want to build something the size of an MRI machine.

5

Why can’t the librarian thunk the books as they are checked in? He/she must be handling them anyway.

6

I can offer no answer to the OP itself, but I found this page at Howstuffworks that describes the function of an ‘electromagnetic tag’: How Does An Electromagnetic System Work?
I believe that one would use an alternating magnetic field to de-magnetise the strips, and in theory it wouldn’t be too difficult to achieve. Just a few big coils. But I’ll leave the details up to someone else.

7

Why can’t the librarian thunk the books as they are checked in? He/she must be handling them anyway.

The machines are too big, and they don’t have the space on the circulation desk for them. There’s one that could fit, because the guts of the device sit on the floor while the “user interface” is desk-mounted, but it wouldn’t be enough for all the librarians to use at once. Further, there are devices in existence that scan and thunk simultaneously, but our branch apparently didn’t warrant any of those according to the bean-counters downtown.

I believe that one would use an alternating magnetic field to de-magnetise the strips

Hmm… alternating magnetic field… I suppose the frequency would be important?

8

OK - here’s another sideways step…

How about you only thunk, say, one in every two carts of books?

OK, so over a long period of time, the ratio of “protected” books to “unprotected” will be 50:50 (I imagine this would take quite some time though, as there must be a hard-core of books that get borrowed regularly, with most getting taken out pretty infrequently). But this would seem pretty good still: anyone determined to steal a book would assume that they are all thunked (or, even if they got wise, would still not know if their’s is safe to steal), whereas those who genuinely forget to check their books out would more than likely have at least one book in their pile that had been thunked.

9

[slight digression]

  1. Unless you are in a small library, a librarian isn’t checking out your book. It’s like a library assistant or a library clerk. We librarians can get uptight about that distinction. After all, we went to grad school and got a half-assed Master’s degree. We’re like doctors with about 1/10 the income. :wink:

  2. Big libraries don’t have security strips in all their books already. It’s just too expensive and time consuming to do so. The system is designed to only stop the very stupid. Stealing a book from the library is about the easiest crime to get away with unfortunately. The biggest problem is that most people don’t think it’s much of a crime. And you would be surprised at the number of “respectable” people (lawyers, doctors, etc.) who have no qualms about stealing or mutilating library materials. And don’t get me started on people who work for Hollywood studios.

[/slight digression]

10

“Circulation Assistant,” I stand corrected. :slight_smile:

Yeah, the librarians generally work at the info desks. And most of our books DO have security strips. The little thunker lights up when we scan 'em.

11

When you work in a building that has over 2 million volumes in it, sticking that little strip down the spine using the bayonet and the bone, (That’s what they’re called in the supply list) can take a long time.

Depending upon the library, there is either a 20-80 or 10-90 ratio involved in circulation. In smaller libraries, 10% of the collection will account for 90% of the circulation. In larger libraries, there is wider demand, but not much.

12

That’s Public Services Assistant to you, buddy.

Actually, I do more reference work than any of the librarians in my department, and more collection maintenence too.

Hmmm… same job, half the pay…

Time to get that MLS!

RE: Security Stripping,

We use the same method. Our holdings are 10 million, and our yearly circulation is more than 13 million. It’s a nightmare.

13

BTW, we’re about 75% barcoded and security stripped throughout the system.

14

Hey, my Masters is at least three-quarters assed. Plus I make at least 50% what most doctors make.

(Of course, I accomplished that by leaving the profession)

Every library I have ever worked in (admittedly only five) has used the hand around method. No clunking.