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Page:Popular Science Monthly Volume 89.djvu/770

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The Electric Thief-Catcher

It rings a bell, takes a photograph of a burglar, and shoots him as soon as it sees his flashlight

IJv 15. F. Miissner

��ALTHOUGH this api^aratiis accoin- A-\ jilishcs some startling ri-siilts, the idea of seleiiiuni-aetiiated Iiurgiar alarms is not altogether new. M. Dafah, a French engineer at J ansae, suggested the use of selenium for this purpose several years ago; others have worked along similar lines.

It may he mentioned here that no atteiTipt has been made to obtain I):itents on this apparatus; its use is unrestricted, and any one with the inclination may cop\- this arrangement for his own use or pleasure.

But what is this Electric Thief- Catcher? How can any machine or electro-mechanical contrivance catch a thief?

In the first place it does not catch him, if b\' catch is meant to ])ursuc and seize, and perhaps to march him to the fKitrol wagon or jjolice station. If by catching is meant to trap, then we may safely say that it does exacth- that, and it can be made to do it as efl'ectivcly as you please. The writer very narrowly escaped being quite effectively caught, when on one occasion this a])paratus sent a thirty-two caliber bullet through his coat-sleeve!

By "as effectively as \ou i)lease" is meant that the "catching" can be ^■ariecl all the way from mercK' sending in an alarm, to frightening the intruder awa>-, or actually shooting him dead.

All that is reiiuired of the burglar is that he possess a light of some kind, if it be onl>' a match or a pocket llash- light, and that its rays fall u])on the acute and e\er wakifui cxc of this hilden apparatus.

This electrical e>e is a selenium cell such as is shown in one of the accom- pan\'ing illustrations. All that it can do is lo record its impressions by sending an impulse to the electro-mechanical brain of the apparatus, when stimulateil by a liglil. Th.il impulse is a surge of electric ( tuK 111 wluii ilic resistance of

��the cell drops, due to the effect of the light. The cause of this curious effect is not yet understood but is being in- \"estigated b>' se\eral men, among whom is Professor F. C. Brown, of the Iowa State Uni\-ersit\-.

The brain is a sensitive rela\-, prefer- ably one such as is used in the Electric Dog, which was described in the March number of Popular Science Monthly. This brain has the power to stimulate an>' one or an\- number of a great \'ariety of electro-mechanical muscles, and to produce a corresjionding \-ariety of actions. In the writer's apparatus one of these was an electric gong, the burglar alarm; another an ordinar\ revob'er whose trigger was pulled by an electromagnet; a third was a camera whose shutter was opened by a cord attached to the .same electromagnet; a fourth, a charge of flashlight powder, which was set off In- the heating of a short piece of tine resistance wire; and on one occasion a hftii was a phono- graph with a specially prepared record, which, without a doubt would frighten (jut of his wits the boldest thief who heard its weird and uncanny warning.

Here, then, we ha\c an electro- mechanical creature, which, hidden from all view, and witii no human agency, will fire a re\-olver, send in an alarm, set off a charge of llash powder, and take the lihotograjih of an\- marauder who prowls about with a light.

Dining tl\e course of a lectiiit- before tile Chicago Electric Club and the National IClectric Light Association, the author in the guise of the burglar stepped lip In the iilatforin in the darkened li'ctini' hall, ll.ishlight in h.ind: till' instant the light fell upon the eye, I he revoU'er began firing, the bell rang, tiu' canu'ra-shutter opened, the llash- lighl powder exploded, and the photo- graph on the following page resulted, 'n another lecture .i phonogr.iph w,is use<I and for five minutes therewasenactinl the

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