This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Ideal Band Stop Filter Transfer Function.svg The transfer function of the Ideal Band Stop Filter showing both positive and negative angular frequencies Vectorised version of IdealBandStopFilterTransferFunction UTC Original bitmap version by IknowNothing SVG version handcrafted by Qef Uploaded with derivativeFX Bandreject filters