sign off

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun broadcasting Term used to describe the closing of a radio or television station's studios and cessation of a broadcasting signal, usually during the overnight hours.
• verb idiomatic To log off; to stop using a computer, radio, etc., especially to stop talking.
• verb broadcasting To cease broadcasting a radio or television signal, usually at the end of a broadcasting day.
• verb followed by “on” to give one's official approval to something for which it is needed

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb cease broadcasting; get off the air; as of radio stations