Door alarm device, has switch linked to chain, which releases alarm by activating switch under effect of break open of door or support, where case and chain are installed on door or support

摘要

The device has a case (1) containing an alarm system and a switch (2) linked to a chain (3). The chain releases an alarm by activating the switch under an effect of break open of a door. The case and the chain are installed on the door. The alarm system has a siren and a resistance capable of consuming electrical energy of the battery that is in parallel with the siren.