"notch filter" meaning in English

{
  "forms": [
    {
      "form": "notch filters",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "notch filter (plural notch filters)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
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          "source": "w"
        },
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          "source": "w"
        },
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          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Signal processing",
          "orig": "en:Signal processing",
          "parents": [
            "Applied mathematics",
            "Telecommunications",
            "Mathematics",
            "Communication",
            "Technology",
            "Formal sciences",
            "All topics",
            "Sciences",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A bandstop filter with a narrow stopband."
      ],
      "id": "en-notch_filter-en-noun-qKufD1wj",
      "links": [
        [
          "bandstop",
          "bandstop"
        ],
        [
          "filter",
          "filter"
        ],
        [
          "narrow",
          "narrow"
        ],
        [
          "stopband",
          "stopband"
        ]
      ],
      "raw_glosses": [
        "(signal processing) A bandstop filter with a narrow stopband."
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences",
        "signal-processing"
      ]
    }
  ],
  "word": "notch filter"
}

{
  "forms": [
    {
      "form": "notch filters",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "notch filter (plural notch filters)",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
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        "en:Signal processing"
      ],
      "glosses": [
        "A bandstop filter with a narrow stopband."
      ],
      "links": [
        [
          "bandstop",
          "bandstop"
        ],
        [
          "filter",
          "filter"
        ],
        [
          "narrow",
          "narrow"
        ],
        [
          "stopband",
          "stopband"
        ]
      ],
      "raw_glosses": [
        "(signal processing) A bandstop filter with a narrow stopband."
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences",
        "signal-processing"
      ]
    }
  ],
  "word": "notch filter"
}