A battery charger for charging different types of battery boards of notebook computers at different time includes a charging box, a plug connector for connecting with a power supplying device and a cable connecting the plug connector with the charging box. This invention presents several possibilities to avoid the spectral pre-echoes existing in decoded signal segment before the energy attack point. Only settings that fit the auditory situation are thereby offered. The wire is wound around the outer surface of the form with at least a portion of the wire disposed in the groove. A temperature exposure signal is asserted to indicate that a high temperature has altered PCM device programming integrity.