A proper subset of a poset A, which subset includes an element less than both of every pair of its members, and includes every element more than each of its members
The collection of cofinite subsets of ℝ is a filter under inclusion: it includes the intersection of every pair of its members, and includes every superset of every cofinite set.
Electronics or software that separates unwanted signals (for example noise) from wanted signals or that attenuates selected frequencies
[orig {{UNIX}}, now also in {{MS-DOS}}] n A program that processes an input data stream into an output data stream in some well-defined way, and does no I/O to anywhere else except possibly on error conditions; one designed to be used as a stage in a `pipeline' (see {plumbing})
A program, which is used extensively by blocking software programs that examines messages and applications for specified critieria and then either allows or denys its operation Filters are common in places such as public libraries and schools and tend to block the chat function of WebCT
A process that modifies a sound by passing some frequencies more readily than others, changing the spectral balance of the sound
A filter is an electrical circuit that allows signals in certain frequency ranges to pass through, and attenuates or blocks all other frequencies There are many types of filters, such as low pass filters, high pass filters, and band pass filters Examples of filters used in machinery monitoring instruments are low pass filters to reject high frequency noise and to prevent aliasing, and high pass filters to reject low frequency noise Variable frequency band pass filters were used in the past to perform spectrum analysis, but they have been largely supplanted by the FFT analyzer
A device that attenuates or increases certain portions of the audio frequency spectrum A bandpass filter passes signal energy only in a specified band and attenuates all others A highpass filter attenuates energy below a certain cutoff frequency A lowpass filter attenuates signal energy above a certain frequency
A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another
A transformation applied to image data in hopes of improving its compressibility PNG uses only lossless (reversible) filter algorithms
Any porous substance, as cloth, paper, sand, or charcoal, through which water or other liquid may passed to cleanse it from the solid or impure matter held in suspension; a chamber or device containing such substance; a strainer; also, a similar device for purifying air