A detector receiver circuit for use as a wake-up detector for detecting an amplitude modulated carrier signal is described. The light source and the lens are mounted in a rotating element. Accordingly, the rocking exercise apparatus can give a larger fitness effect by complicating the movements while being small and inexpensive. The hard carbon-based film has a surface section which contains at least one of nitrogen and oxygen in an amount ranging from 0. If the torque generated by the gas turbine is insufficient, the control unit controls the motor so as to carry out a helper motor operation for increasing the torque.