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A line trap ( high-frequency stopper ) is a maintenance-free inductor , mounted inline on high voltage AC transmission power line s to prevent the transmission of high frequency ( 40 kHz to 1000 kHz ) carrier signals of Power line communication to unwanted destinations .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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