A wireless communication system has a plurality of wireless communication devices capable of communicating with one another directly without the intervention of another device, and a wireless control unit which accommodates these wireless communication devices. The releasable stud includes a stud body and a first fastening mechanism coupled to the stud body. The active delay line and phase shifter separately receive the output signal of the DUT. In one embodiment, the control system includes a pressure transducer, first and second multipliers, and first and second flow controllers. In an example embodiment, the beam current reaching the substrate is reduced by establishing an opening ratio of 50% or less for the pattern as a whole as defined on the reticle. The drain of the second MOSFET is connected to a node between the inductor and the capacitor via a resistor.