A power system includes a power semiconductor devices; a control circuit outputting first firing signals each being for a corresponding power semiconductor device, and outputting first activation response signals each being associated with a corresponding power semiconductor device. In one example, the shared amplification path can include a low noise amplifier and an attenuator. Finally, another etching process is performed to etch through the hard-mask layer and the dielectric layer and form the damascene structure in the dielectric layer, wherein this etching process utilizes the mixed gas having chlorine, such as O2Cl2. The braking unit of each of the castor assemblies includes a bushing, a housing, a control shaft, and a braking member.