A programmable frequency receiver includes a slicer for receiving data at a first frequency, a de-multiplexer for de-multiplexing the data at a second frequency, a programmable clock generator for generating a clock at the first frequency, and first and second resonant clock amplifiers for amplifying clock signals at the first and second frequencies. An oxygen concentration sensor that outputs a continuous value corresponding to the oxygen concentration of the exhaust gas flowing through the exhaust passage is provided in the exhaust passage. As a result, the Hall ICs are accurately positioned with respect to a permanent magnet disposed in a shaft side of the throttle valve, thereby improving an accuracy of detecting the rotation angle of the throttle valve. The fluidized-bed reactor is configured to include two distinct regions, namely a lower aerobic region and an upper anoxic region, during normal operating conditions. The trailing edge retention system may be configured to automatically and selectively retain one or more second sheets in the stack by applying a force to a trailing portion of at least one second sheet, thus allowing the feed roll and retard system to be separated during much of the feed cycle. The PFC circuit comprises a valley-filled PFC circuit and a harmonic compensation circuit, whose output signal is supplied to the current control circuit.