Dibenzopyrone derivatives which possess depressant and/or antihypoxia activity are 7,8,9,10-tetrahydro-6-oxo-6H-dibenzo[b,d]pyranyloxy-propanes having the formula (1): ##STR1## where R represents hydrogen or (C.sub.1 -C.sub.4) alkyl; where A represents chlorine or hydroxyl; and where B represents hydrogen, (C.sub.1 -C.sub.4) alkyl, 7-coumarinyl, phosphono, phenyl, or phenyl substituted with amino, dimethylamino, hydroxyl methoxyl, carboxyl, carboxymethyl, or 2-carboxyethenyl. Also included are pharmaceutically acceptable salts of the compounds. Compounds of this invention are useful as sedatives or for the protection of warm blooded animals from the effects of oxygen depreviation.
The present invention provides a diagnostic system for an internal combustion engine which detects abnormalities of input/output objects used in controlling operation of the engine when the engine is in respective predetermined operating conditions, and carries out respective predetermined fail-safe actions when abnormalities of the input/output are detected. When an abnormality of the input/output objects was detected on the last occasion and has also been detected on the present occasion, and at the same time it is determined that a change in the operating environment of the engine has occurred between when the abnormality was detected on the last occasion and when it has been determined on the present occasion, occurrence of the abnormality is finally determined.
