(a) What idea leads to the digital signal which filters directly in the time domain and thus avoids transformation into the frequency domain and back again my means of the FFT?
(b) Explain the principle of digital filters on the basis of the overlapping of Si-shaped pulse responses of all discrete measurements (see Illustration 209).
(c) A filter restricts the bandwidth and for this reason a correspondingly long lasting discrete pulse response also occurs in the case of digital filters. What signalling processes are required to produce a longer lasting discrete pulse response "artificially" from a δ-pulse?