Continuous Wave (CW), the modulation mode of switching a carrier on and off to encode information, or sending Morse code tones over AM or FM modes. Questions that are about Morse code alone and not about radio at all, such as a question asking about some Morse code in a movie, should use the "morse-code" tag instead. Questions about keying a radio should use this tag. Questions about Morse-code-related radio procedures, e.g. Q-codes, should use this tag.