The present invention relates to the glass substrate for an information recording medium comprising the following glass components: SiO2: 52 to 67; Al2O3: 8 to 20; B2O3: 0 to 6, with these three oxides FMO: 70 to 85; Li2O: 0. In a printing operation the real value of the web tension is regulated to a predetermined desired operating value of the web tension. Balancing the momentum of the probe holder reduces parasitic oscillations in the apparatus thus enhancing performance. The data reading method further includes when data read from one of the physical pages of one of the physical page groups cannot be corrected by using an error checking and correcting circuit, updating the threshold voltage set corresponding to the physical page group. The generator also includes a controller, which may include a microprocessor, that is adapted to receive a tissue impedance signal andor a waveform zero crossing signal.