Security techniques and security mechanisms for wireless networks that transmit content such as advertisements. The image recognition process includes the following steps: an image capturing step for capturing image frame data by using an image capturing unit; and a lane line recognition for analyzing the image frame data for determining the lane lines. The magnitude comparator includes many non-least comparator cells and a P-channel transistor. The entrance surface of the prism is configured as a curved surface with negative power which is rotationally symmetrical with respect to the optical axis. A catalyst may be placed in a center of a toroidal recirculation chamber of the laser and may have integrated filters to prevent catalyst particulates from coating the chamber optical windows. The door edge protection member is driven via an eccentric lever mounted rotatably in the door.