sign off

verb

To log off; to stop using a computer, radio, etc.; especially, to stop talking.
“He finished the conversation and signed off.”
To cease broadcasting a radio or television signal, usually at the end of a broadcasting day.
“Before he signed off the radio station for the night, the disc jockey played the National Anthem.”
to give one's official approval to something for which it is needed, especially by a signature.
“Once the vice-president signs off on the project, we can start construction.”
“The town council, which closed the funicular last December for health and safety reasons, has yet to sign off the completion of £72,000 worth of remedial works to a retaining wall.”
To use a valediction, such as the end of a letter or broadcast.
“Boys of about fourteen to sixteen opened their letters to each other with 'manly' forms of address such as 'Amice' (My friend). They signed off with 'Vale' (Farewell), or 'TT' (Totus Tuus, All yours).”
“Lee scripted, art-directed, and edited most of Marvel's series, moderated the letters pages, wrote a monthly column called "Stan's Soapbox," and wrote endless promotional copy, often signing off with his trademark phrase "Excelsior".”