A clutch disc, particularly for use between a pressure plate and a counterpressure plate in a friction clutch which is installed in the power train of a motor vehicle, has two friction linings flanking resilient carriers mounted on a washer which has a hub connectable with a torque receiving part, such as the input shaft of a change-speed transmission. In a first mode, the buffer circuit is configured to provide a low output impedance, characteristic of a digital buffer. The processing mode may be established by placing an enable indication in a control register into an enabled state and by setting a first operating mode indication and a second operating mode indication in a segment descriptor to predefined states. An actuator makes blocking engagement with the engine valve having been opened, to thereby hold the engine valve in an open state. However, conventionally, when applying a simple ac voltage, the transition sometimes does not take place, and when it does take place, the transition time is very long, and display defects due to alignment defects tend to occur. The method comprises the steps of transmitting a set of optical signals through a network, each of the optical signals having a respective wavelength; and tracking changes to said set of signals by passing each of the signals through a filter having a bandpass function, and dithering the filter bandpass about the wavelengths of each of said set of signals to generate filter output signals.