A method and system for checking the validity of a sequence of input characters according to the syntactical rules of a selected language is provided. During continued use of the catheter the power control system periodically determines the difference between the stored datetime and the current datetime. Packet flow arrivals are quantified by counting arrivals per unit time, or by measuring an inter-arrival time between flows. A magnitude of the first force on the firing pin is inversely proportional to the distance the firing pin moves away from the pre-firing position. Forming the gate electrode may include forming a polysilicon first gate electrode layer and forming an amorphous silicon layer over the polysilicon first gate electrode layer.