Before revision: Detection is usually based on the frequency of the carrier signal, as in the familiar frequencies of radio broadcasting, but it may also involve filtering a faint signal from noise, as in radio astronomy, or reconstructing a hidden signal, as in steganography.
After revision: Detection is usually based on the frequency of the carrier signal, as in the familiar frequenMorse_codecies of radio broadcasting, but it may also involve filtering a faint signal from noise, as in radio astronomy, or reconstructing a hidden signal, as in steganography.