A system and related method for increasing or decreasing the range of a pico cell station. The method further includes discontinuing transmission of the compressed muted audio data and transmitting compressed audio data via a second compression scheme, wherein the first transmitting step causes the wireless microphone unit to consume less power per unit of transmission time than the second transmitting step. Under this configuration, the cavitation device can freely generate a partial cavity or a super cavity on the surface of the underwater moving body. A plurality of car pairs are mounted to the hub for longitudinal movement along the hub. The interface circuit further reduces the coupling of noise generated from the operation of the discrete time circuit to the preceding continuous-time circuit.