A memory controller includes a bus driver that allows the controller to support both a semiconductor memory device supporting a low power double data rate 3 transmission method and a semiconductor memory device supporting a low power double data rate 4 transmission method. The elastic stop lug can be pressed to retreat in the sidewall so as to let the shank of a bolt to pass over, and then recover to its original position to stop the shank of the bolt not to fall out of the opening, so the bolt can be held in the engage groove without using a finger so that a worker can conveniently fix the lamp socket on a vehicle body. Product information may additionally or alternatively be obtained or derived based on popularity data. Whether opaque or transparent, a total weight of the plate is less than approximately exactly 50 kgM2. The personal defense device may optionally include a one or more cameras and a wireless communication link for transmitting status information, images and audio to a monitoring station.