Theft alarm for displayed goods - phototransistors shielded by goods and exposed to light when goods removed

摘要

A method for protecting displayed articles from theft, in which a number of photoresistors are set up with the articles in such a way that the photoresistors are screened from incident light by the displayed articles. Removal of an article allows light to reach one or more photoresistors; the resistors are connected in parallel and included in an alarm circuit which is thus triggered by the removal of any of the articles. The articles (4) may be set out on a board (3) provided with a number of sockets (6) wired in parallel, the articles being provided with feet (5) to raise them a little above the surface; one or more photoresistor is plugged in under each article to protect it from the light of a lamp (7) suspended above the display.