A first well of the same conductivity type as that of a semiconductor substrate and a second well of a conductivity type opposite to that of the semiconductor substrate, are formed in the semiconductor substrate. Also a liquid crystal electro-optical device comprising a liquid crystal layer disposed on a substrate is included, wherein the transmission mode or the dispersion mode of an incident light is selected by an electric field applied to the liquid crystal layer in the direction parallel to the liquid crystal layer. Active devices can be discovered by the discovery node through a serial pinging mechanism which populates the MIB of the discovery node with IP andor MAC addresses of all the devices on the network. With the composing elements of a motion information module, an input module, an output module, a timer module and an information processing module, the present invention can accurately determine whether the vehicle under surveillance is in idle state and for how long it is in the idle state, and send an alarm signal automatically.