A reactive network that is designed to provide specified attenuation to signals within certain frequency limits; basic filters are termed low-pass, high-pass, bandpass, and band-reject designs.
"Thanks so much for converting my 42-year old Bar Mitzvah audio-tape to CDs. For such a solemn occasion, I couldn't stop laughing! Hearing my high-pitched, Texas-twanged Hebrew is such a treat; I would never have recognized that the boy on that tape is me. Surely my parents and sons will get a kick out of hearing this voice from my past."