The optical characteristics of a banknote are measured by using first and second sets of optical devices positioned on respective sides of the banknote path. or lower and can be stably supplied by bubbling in a chemical vapor deposition method or an atomic layer deposition method, a precursor for forming a europium-containing thin film based on the compound, and a method for forming a europium-containing thin film using this precursor. The pair of substrates and the insulator are provided so as to be slidable. Also disclosed is a data carrying compact disc which incorporates security means to allow a first reading of the data of the disc, but to prevent such reading thereafter. The search circuit generates a plurality of address values that correspond to unoccupied storage locations within the memory, and the plurality of address values are queued within the first-in-first-out storage circuit to enable the address values to be read in succession by an external device. Therefore, the low power mode may be effectively implemented.