BSF stands for “Band-Stop Filter,” also known as a “notch filter.” It’s an electronic filter designed to pass a range of frequencies while attenuating or blocking frequencies within a certain “stopband.” In other words, a band-stop filter allows most frequencies to pass through, except for a specific range of frequencies that it suppresses. This type of filter is used to eliminate or reduce interference caused by specific frequencies, often referred to as “notches,” while preserving the overall frequency spectrum.