Abstract: By combining a number of integrators with periodically switching means, which are sensing an input signal during circularly successive time intervals, sampled values are available for some of the latest time intervals sampled with a sampling frequency. By switching these values in a successive manner to an analog arithmetic circuit, it is possible to obtain an output signal with useful band-pass and band-reject properties depending on the sampling period and the arithmetic operation. According to one preferred embodiment, the output signal is the mean over the latest time intervals, giving an averaging system which, contrary to RC circuits, has a strictly limited memory. According to another preferred embodiment, the output signal is the different between the outputs of two integrators.