There’s no more wondering how the STI Stopper II, a cover which helps prevent false fire alarms, does its job. Safety Technology Intl. Inc. (STI) of Waterford, Mich. has placed a video on its website demonstrating how the protective cover operates. The Stopper II device mounts directly to the wall over an existing pull station. When it is lifted, a self-contained alarm sounds which draws immediate attention to the area.