Abstract: A cooling medium temperature monitoring system for a rotary electric machine for cooling stator coils by as cooling medium flowing in a plurality of cooling medium passages provided in the stator coils, has a plurality of temperature detectors for measuring the temperatures of the cooling medium in the outlets of the plurality of cooling medium passages; and a circuit for setting the temperature warning value at a value which is responsive to the output of a generator, and a calculator circuit for comparing the detected outputs of the temperature detectors with the set value of the warning value setting circuit to generate an alarm signal when the output of any one of the detectors exceed the set warning value.

Abstract: A semiconductor device includes a semiconductor layer on one side of a semiconductor body to define a pn-junction therebetween, diffraction gratings formed at a distance from each other on the top of said semiconductor layer, and electrodes formed between the diffraction gratings on the top of said semiconductor and formed on the other side of the semiconductor body.

Abstract: A semiconductor optical device includes a semiconductor body, a light emitting layer formed on the body to form a pn junction therebetween, a semiconductor layer formed on the light emitting layer and a diffusing region formed in the semiconductor layer to define a pn junction therebetween and electrically connected to the light emitting layer. Three electrodes are respectively provided on the semiconductor body, semiconductor layer and diffusing region, which are selectively operated.