Electronics: To Catch a Thief

Desperate to reduce book thefts, the nation’s 60,000 libraries have tried everything from shelving their books behind iron fences to putting in ceiling mirrors to spot browsers stuffing books into clothing or briefcases. Nothing seems to work: the Library Journal estimated not long ago that thieves take anywhere from 200 to 500 books a year from the average library, and library officials glumly admit that book thefts now cost them an estimated total of $25 million a year.

A Metal Insert. The answer to the librarians’ plight may lie in an electronic device demonstrated last week in Flint, Mich. Playing the part of a thief, a Flint librarian slipped a library book under his coat, then walked boldly to the exit. There was a loud click as the turnstile locked, then a buzzing noise as the librarian was alerted. Even as the “thief” sheepishly explained that he “forgot” to sign out his book, a patron whose book had been properly checked out strode easily through the same turnstile.

Invented by Emmanuel Mitchell Trikilis, a self-taught Columbus engineer, the “Sentronic” book detector works on the ancient principle of magnetism. A sliver of magnetized metal is hidden somewhere in a book’s spine or binding, and the librarian who checks the book out simply demagnetizes the metal insert by passing the book through a coil carrying an electric current. If a thief bolts for the exit instead of the check-out desk, the magnetized metal inside his book is detected by an instrument that trips a solenoid hidden at the door; the turnstile is automatically locked and the librarian alerted. A sign over the door explains all with a succinct message: “If turnstile is locked, please report to loan desk.”

A Great Deterrent. Trikilis’ system is not a perfect burglar finder, and it cannot foil the determined thief who tosses a stolen book out a window. But drawbacks are few, and along with a similar setup made by Bro-Dart Industries of Newark, N.J., the Sentronic sentry is being studied by libraries across the U.S., from the Harvard University Medical School library to San Quentin prison library.

Flint Librarian Ransom L. Richardson is convinced that the system is worth the expense—$6,740 a year for rental of Sentrons plus $4,500 for installation of equipment for four turnstiles. “Even if we just cut our losses in half,” says Richardson, “we’ll be ahead.” The Grand Rapids library, which used to lose between $10,000 and $15,000 a year on stolen books, began slipping Trikilis’ Sentron devices inside their books eight months ago, has not lost one of its treated volumes since. Says Grand Rapids Librarian Donald W. Kohlstedt: “The deterrent value of the system alone is as great as the detection.”