1. A digital filter for separating signals occupying separate frequency portions of a contiguous range of input signal frequencies, comprising: a source of input signal; delaying means, including a shift register coupled to said source and having a plurality of signal taps including a center tap; respective signal weighting means, coupled to ones of said signal taps, including a center tap weighting means, for weighting signals occurring at said taps; means, coupled to said signal weighting means, excluding said center tap weighting means for producing at a first output port a signal which is a sum of tap-weighted signals; first signal combining means having a first input coupled to receive said sum of tap-weighted signals and a second input coupled to said center tap weighting means for combining applied signals in a first sense to produce output signals occupying a relatively high frequency portion of said contiguous frequency range; and second signal combining means having a first input coupled to receive said sum of tap-weighted signals and a second input coupled to said center tap weighting means for combining applied signals in a second sense to produce output signals occupying a relatively low frequency portion of said contiguous frequency range, wherein the frequency responses of said first and second signal combining means are completely transfer functions.