Early history of the high-fidelity finite-impulse-response filter

The little-known efforts of some 19th-century digital filter designers are reviewed. Their object was to separate a precise curve from added random noise, and as such their work is relevant to certain current applications such as inertial navigation. Several classical design methods are described, and examples are given. The work of G.F. Hardy is of particular significance, as it introduces a method which can be extended to the point that, with the aid of a computer, it is capable of designing modern high-fidelity filters.