An optical disc apparatus varies a tilt angle of an optical pickup from inward to outward of an optical disc, and stores a then obtained TE signal in a memory of a control circuit. Audio feedback techniques are provided to convey audio cues about navigable data. The memory cell array includes a plurality of blocks in each one of which the memory cells are arranged. The test system transmits the unit test cases to the component systems, receives test results, and validates the test results to ensure that the network system functions properly.