Active tags are disclosed. According to one aspect of the present invention, an active tag is made similar to a shell in shape. The tag includes two parts, one is referred to as a cover and the other one is referred to as a base. The base includes a trigger tip (e.g., a reset switch) that is engaged when the two parts are closed. In an exemplary application, the needle of the cover part goes through a piece of garment and is engaged into the cover. These two parts can be disengaged by a detacher that is typically controlled by a casher (e.g., at point of sale). One of the important features in the present invention is that the tag is active, which means the shell tag will set off an alarming audio if disengaged improperly or without authorization.