An alarm system having the capability to self-adjust or self-calibrate itself is disclosed. The center electrode and the surface-gap ground electrode define a radial spark gap therebetween. An image pre-processing circuit in which a 2-D image formed by the video data input is captured, and includes a low pass filter for performing noise filtering of said video input. The surface portion of the top protective layer includes electrical contact pads that are electrically connected with electrical contact pad extensions and with the integrated circuit. After forming modified regions SD1, SD2 at positions closer to the rear face 21 but before forming modified regions SD4, SD5 at positions closer to the rear face 21 while using the front face 3 as a laser light entrance surface, the modified region SD3 is formed at the intermediate position by irradiation with laser light modulated according to a modulation pattern including the quality pattern J. The indicator is structured to indicate the corresponding throttle notch position.