Optical bandpass filters are designed to transmit a specific waveband.  They are composed of many thin layers of dielectric materials, which have differing refractive indices to produce constructive and destructive interference in the transmitted light

RF filters and microwave filters are devices that pass or reject signals by frequency. Basic types include bandpass filters, band reject filters, low pass filters, and high pass filters

Signal filters block or decrease (attenuate) unwanted frequencies or signal wave characteristics

Active filters are electronic filers that use active components such as voltage amplifiers or operational amplifiers. The amplifier shapes and stabilizes the behavior of the filter, and serves as a buffer interface to the driven component

Industrial filtration equipment is used to filter, thicken or clarify a mixture of different elements

Active band pass filters are used to attenuate frequencies below and above a range of frequencies (i.e., the bandwidth or passband of the filter

Camera filters provide a range of optical filtering effects in scientific, research, and industrial applications

Liquid filtration elements are used to remove impurities from liquids. They are used in water treatment systems and fluid processing applications.

Filtration media and elements are designed to remove suspended particles from a process stream. This product area includes bulk filter media, cartridges, housing-only products, and housing and filter assemblies. 

Digital filters use digital signal processing (DSP) to perform numerical calculations on sampled values of a signal

Passive filters are implemented using only passive components such as resistors, capacitors and inductors. These filters do not produce any amplification of the input signal

Industrial air filters reduce the number of particles in the air that passes through them. 

Long pass filters transmit a wide spectral band of long wavelength radiation while blocking short wavelength radiation. Short pass filters transmit a wide spectral band of short wavelength radiation and block long wave radiation

Electromagnetic (EMI) filters and radio frequency interference (RFI) filters purify signals by attenuating the high-frequency RFI (typically 150kHz and up) and passing the low frequency EMI

RF band pass filters are active or passive circuits that pass signals from a specific frequency band and reject signals from out-of-band frequencies. Surface acoustic wave (SAW) filters, crystal filters, and cavity filters are types of band pass filters