The Arkray Widal S. Typhi AG Set H,O,A(H)&(H) is a diagnostic test kit used to detect Salmonella antibodies in the blood to diagnose typhoid fever. The "H" antigen is for the flagellar antigen, and "O" is for the somatic antigen, with "A(H)" and "A(H)" referring to specific Salmonella serotypes like AH, AO, BH, BO, CH, or CO. The set uses a killed bacterial suspension to identify specific antibodies produced by the body in response to a Salmonella infection.