Abstract: A pet door assembly has a frame having an opening defined therein, a flap mounted to the frame for covering the opening and movable to allow a pet to pass therethrough, a cover removably mounted to the frame to cover the opening and prevent passage through the opening, a detector mounted to the frame for detecting when the cover has been removed, and an alarm sound generator mounted to the frame for generating a sound in response to the detector detecting removal of the cover. In another embodiment, there is a cover for a pet door having an alarm which cover may be retrofit onto a pet door assembly of a type having a frame with an opening defined therein, and a flap for covering the opening. The cover is sized to replace an existing cover for the door, and has an alarm assembly mounted on it. The alarm assembly has a detector for detecting when the cover has been removed, and an alarm sound generator for generating a sound in response to the detector detecting removal of the cover.

Abstract: The computer robot arm chess game assembly is provided with a chess board, magnetized chess pieces, auxiliary parking locations for the chess pieces, and an articulated radially moving robot arm. The robot arm can perform all the functions of an opponent including setting up the chess board, captures, promotions, castling, etc. The chess board and parking locations include magnetic members to not only activate resilient switches but further to spatially position the chess pieces for accurate location to assist the robot arm. Among the other interesting features, the robot arm can show emotional characteristics which can be accompanied by appropriate sounds and lights contemporaneous with a significant occurrence during the progress of the chess game.