If we wish to implement this filter as a digital filter, we can apply the bilinear transform by substituting for the formula above ; after some reworking, we get the following filter representation:

By having two different temporal positive feedback loops or “ dual-time switches ” allows for ( a ) increased regulation: two switches that have independent changeable activation and deactivation times ; and ( b ) linked feedback loops on multiple timescales can filter noise.

Bistability can only arise in biological and chemical systems if three necessary conditions are fulfilled: positive feedback, a mechanism to filter out small stimuli and a mechanism to prevent explosions.

Overblocking: A filter that is overly zealous at filtering content can be described as over blocking.

Over blocking can filter out material that should be acceptable under the filtering policy in effect, for example health related information may unintentionally be filtered along with porn-related material because of the Scunthorpe problem.

Content filtering in general can " be bypassed entirely by tech-savvy individuals " Blocking content on circumvention advice " not ... guarantee that users won't eventually be able to find a way around the filter.

The two techniques can be used together with the packet filter monitoring a link until it sees an HTTP connection starting to an IP address that has content that needs filtering.

The packet filter then redirects the connection to the web-proxy which can perform detailed filtering on the website without having to pass through all unfiltered connections.

A non-causal filter can usually be changed into a causal filter by adding a delay to it.

An " unstable " filter can produce an output that grows without bounds, with bounded or even zero input.

Filters can be represented by block diagrams, which can then be used to derive a sample processing algorithm to implement the filter with hardware instructions.

Filtering, particularly in non-realtime work can also be achieved by converting to the frequency domain, applying the filter and then converting back to the time domain.

This is a fast, O ( n log n ) operation, and can give essentially any filter shape including excellent approximations to brickwall filters.

Feedback oscillator circuits can be classified according to the type of frequency selective filter they use in the feedback loop:

Product mixers can either up-convert or down-convert an input signal frequency, but they are more commonly used to down-convert to a lower frequency to allow for simpler filter designs, as done in superheterodyne receivers.

Any residual harmonics can be removed using a further filter.

A linear time-invariant ( LTI ) filter can be uniquely specified by its impulse response h, and the output of any filter is mathematically expressed as the convolution of the input with that impulse response.

Among the time-domain filters we here consider, there are two general classes of filter transfer functions that can approximate a desired frequency response.

The impulse response completely characterizes the response of any such filter, inasmuch as any possible input signal can be expressed as a ( possibly infinite ) combination of weighted delta functions.

The 3 dB bandwidth of an electronic filter or communication channel is the part of the system's frequency response that lies within 3 dB of the response at its peak, which in the passband filter case is typically at or near its center frequency, and in the lowpass filter is near 0 hertz.

* Filtration differs from removal of magnetic contaminants from fluids with magnets ( typically lubrication oil, coolants and fuel oils ), because there is no filter medium.

1-channel protein domain | domain s ( typically four per channel ), 2-outer vestibule, 3-Potassium channel # Selectivity filter | selectivity filter, 4-diameter of selectivity filter, 5-phosphorylation site, 6-cell membrane.

Lubricants for machines that regularly generate debris or contaminants such as automotive engines typically contain detergent and dispersant additives to assist in debris and contaminant transport to the filter and removal.

These typically consist of an excitation filter selecting the range of excitation wavelengths, a dichroic mirror, and an emission filter blocking the excitation light.

When the area of the sampling spot ( the size of the pixel sensor ) is not large enough to provide sufficient spatial anti-aliasing, a separate anti-aliasing filter ( optical low-pass filter ) is typically included in a camera system to further blur the optical image.

This is the form for a recursive filter with both the inputs ( Numerator ) and outputs ( Denominator ), which typically leads to an IIR infinite impulse response behaviour, but if the denominator is made equal to unity i. e. no feedback, then this becomes an FIR or finite impulse response filter.

A bandpass filter typically has two stopbands.

This higher-order function is typically named filter in functional programming languages.

Multi-photon events are, however, typically more drawn out in time ( photons did not arrive exactly at the same time ) than single photon events and pulse-length discrimination can thus be used to filter most of these out.

This 1984 Software Radio was a digital baseband receiver that provided programmable interference cancellation and demodulation for broadband signals, typically with thousands of adaptive filter taps, using multiple array processors accessing shared memory.

Rioters typically wear face masks, scarves, and other headgear not only to conceal their identity, but also to filter tear gas.

Because particles accumulate in the oil, it is typically circulated through an oil filter to remove harmful particles.

Switching occurs at a very high frequency ( typically 10 kHz — 1 MHz ), thereby enabling the use of transformers and filter capacitors that are much smaller, lighter, and less expensive than those found in linear power supplies operating at mains frequency.

The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine's oil system and cause wear on other parts before being trapped by the oil filter.

A reconstruction filter is typically used in PCM decoding systems, much the same way that bandwidth-limiting filters are normally used in PCM encoding systems.

Fluorescent black light tubes are typically made in the same fashion as normal fluorescent tubes except that a phosphor that emits UVA light instead of visible white light is used, and the clear glass envelope of the bulb has a deep-bluish-purple optical filter coating which blocks almost all visible light.

On Amiga 1000 ( and first Amiga 500 and Amiga 2000 model ), the power LED had no relation to the filter's status, a wire needed to be manually soldered between pins on the sound chip to disable the filter.

Some libraries that employ content-control software allow the software to be deactivated on a case-by-case basis on application to a librarian ; libraries that are subject to CIPA are required to have a policy that allows adults to request that the filter be disabled without having to explain the reason for their request.

Another major criticism point has been that although the filter is claimed to stop certain materials, the underground rings dealing in such materials will not be affected.

This is especially useful in environments where the computer is being supervised and the content filter is aggressively blocking Web sites that need to be accessed.

Packet inspection filters do not initially interfere with the connection to the server but inspect the data in the connection as it goes past, at some point the filter may decide that the connection is to be filtered and it will then disconnect it by injecting a TCP-Reset or similar faked packet.

A filter may also be described as a difference equation, a collection of zeroes and poles or, if it is an FIR filter, an impulse response or step response.

The output of a linear digital filter to any given input may be calculated by convolving the input signal with the impulse response.

A digital filter may be described in the z plane by its characteristic collection of zeroes and poles.

This leads to the Great Filter, which notes that since there are no observed extraterrestrial civilizations, despite the vast number of stars, then some step in the process must be acting as a filter to reduce the final value.

The output signal may be obtained by removing the other signal components with a filter.