Shoplifting detection unit - uses coaxial cable threaded through valuable items, e.g. for coats.

摘要

Both ends of a continuous coaxial cable (3) are plugged into connectors (4',5') on the alarm unit. A relay (A) will de-energise if the cable is broken, and another relay (B) will energise is the screen of the cable is shorted to its core. If the first relay (A) de-energises or the second (B) energises, their contact sets (a1,b1) will energise a third relay (C) which has a hold on contact set (C1) and a contact set (C2) which powers audible (8) and visible (7) alarm devices. An assistant may temporarily disable the unit by inserting a wired plug (10), e.g. while removing a solid item, but if the plug is not removed within a preset time, a time delay relay (D) operates another alarm (11). A master key-operated switch (6) may be used to switch the unit off when not required.