Abstract: A notification device for use with a plurality of barriers corresponding to a plurality of openings in a container having an interior space accessible through said openings. Each barrier having a closed position in which it closes a corresponding opening and an open position to provide access to said interior space. The notification device providing a notification signal when one or more of said barriers has been moved from the closed position toward said open position. The notification device comprises: a power supply; a sensor mounted adjacent each barrier and corresponding opening for sensing when that barrier is not in a closed position; and a signal generator having multiple signal generation modes for generating a unique notification signal in each mode in response to each sensor.