A system and method are provided for organizing a number of digital images. The fuel discharge member is fixed on a fuel supply conduit, and comprises: a main body having an internal space which communicates with a fuel passage in the fuel supply conduit, fuel discharge outlets which communicate with the internal space, and a trailing edge. Upon receiving the request signal, the terminal sends, at the probability indicated by the request signal, a response signal including the identification information uniquely allocated to the terminal. The light at the first wavelength mixes with the light at the second wavelength to form light of a third wavelength, which may be white light or another color. The secondary acoustic signal is transmitted one of continuously, synchronously intermittently, and asynchronously intermittently, and does not interfere with the primary optical signal.