Analogue filter

This article is about the history and development of passive linear analogue filters used in electronics. For linear filters in general see Linear filter. For electronic filters in general see Electronic filter.

Analogue filters are a basic building block of signal processing much used in electronics. Amongst their many applications are the separation of an audio signal before application to bass, mid-range and tweeter loudspeakers; the combining and later separation of multiple telephone conversations onto a single channel; the selection of a chosen radio station in a radio receiver and rejection of others.