A permanent magnet generator having the unique feature of a speed proportionally adjusted air gap for self-regulation of coil output voltage over a wide range of operating rotational speed of a steam turbine to which the invention is coupled. A decision is made as to whether or not a remaining usable capacity in the recording medium corresponds to longer than a predetermined time during the recording of the first video-contents information on the recording medium. The method includes the step of loading the first shotmeter with the material. Detecting can include identifying a protected access to a memory location by a first thread of the threads and identifying an unprotected access to the memory location by a second thread of the threads.