sign off

verb4

1. •
   To log off; to stop using a computer, radio, etc.; especially, to stop talking.

   • He finished the conversation and signed off.
2. •
   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.
3. •
   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.
4. •
   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). — 2011