An NC data service business is created, by making use of a numerical control data service provider company PC1 provided with associated devices necessary for NC data preparation such as a CAD system, a CAM system, a dedicated NC post processor, an NC machining simulator and an NC machining unit. The system includes a constant current source circuit that includes a bias circuit that outputs a bias signal and a switch circuit that has a switch input coupled to receive the bias signal, a switch output, and a switch control that is coupled to receive an input signal. Moreover, the shim prevents the resilient material from taking a set and the flexible connector from draping when operating under hot andor high load conditions. If fraud or leakage is detected in the distribution network, the system may schedule a follow-up andor field investigation to investigate and fix the fraud or the leakage in the distribution network. When the light emitting element of the first light guide plate is lit, different color lights are produced, such that a light transmission effect of single-color light or mixed multiple-color light occurs at the surface of the keypad corresponding to the first light guide plate.