The invention provides improvements in reconstructive imaging of the type in which a volume is reconstructed from a series of measured projection images generated by projection of a point x-ray source, positioned at a distinct focus, through the volume to a plane at which the respective projection image is acquired. A policy and charging rule function and mobile communication system are also disclosed in the present invention, thereby enabling the system to save network resources and increase the utilization of network resources. The shunt switch is connected to the signal path at a point between the signal switch and the load circuit.