[band-pas, -pahs] 
| a filter that attenuates all frequencies except those of a specific band, which it amplifies. |
band-pass filter
arrangement of electronic components that allows only those electric waves lying within a certain range, or band, of frequencies to pass and blocks all others. The components may be conventional coils and capacitors, or the arrangement may be made up of freely vibrating piezoelectric crystals (crystals that vibrate mechanically at their resonant frequency when excited by an applied voltage of the same frequency), in which case the device is called a crystal band-pass filter or a monolithic filter.
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