A discharge lamp includes a discharge tube containing electrodes, and base sections. The base sections have terminals for connecting to external power lines, and internal power lines for connecting the terminals to the electrodes within the discharge tube. Information generation devices that generates information to be output to outside are provided within the base sections. Superimposition circuits that superpose the information, generated by the information generation devices, on the internal power lines within the base sections are also provided within the base sections. The information generation devices include sensors and generate information based on output of the sensors. A receiving circuit extracts and receives the information, superposed on the internal power lines, from the external power lines connected to the internal power lines. Thus, information generated on the discharge lamp side can be transmitted to outside with a simple construction.