Definition
An electronic circuit that allows signals within a specific range of frequencies to pass through while blocking frequencies above and below that range.
Plain English
A filter that lets through only the frequencies you want, and rejects anything higher or lower.
Context Anchor
Seen in discussions of aircraft radios, navigation receivers, audio systems, and other avionics that must separate one useful signal from unwanted signals.
Derivation
The name describes the function: a 'band' is a range of frequencies, and the filter lets that band 'pass.' Frequencies outside the band are blocked.
Why Pilots Care
Maintains clear radio communications and navigation signals by removing interference that could mask critical ATC or navaid transmissions.
Analogy
Think of a window screen that only lets through bugs of a certain size — anything smaller falls through, anything larger gets caught, and only the middle range comes in.
Intuition Check
A band-pass filter is not a filter that cleans dirt out of something. It selects a range of signal frequencies and reduces the rest.
Example Sentence 1
The VOR receiver uses a band-pass filter to accept the navigation frequency and reject nearby radio traffic.
Example Sentence 2
During the avionics check, the technician confirmed the band-pass filter was passing only the correct VOR frequencies.