A technology that can adaptively control an access mode according to a shared band or an unlicensed band used by an adjacent communication system. The truss boom includes longerons, battens, and diagonals A fixed ladder shaped structure is formed by a plurality of fixedly coupled battens which interconnect two adjacent longerons. A hollow support member covers the top surface of the base member and the fan module. The passive extinction occurs when the electric arc is conducted through the filament extending into the press seal. The armature assembly when moved to its first position causes the pass through circuit to be coupled into a circuit.