DuckCorp Dico

Found one definition

1.                 From English - German Ding/FreeDict dictionary ver. 1.9-fd1:
                   
   
   
                   
                     
   ring-back /ɹˈɪŋ bˈak/
   Intern-Rückfrage <fem>, Rückfrage <fem> [telco.]
            Note: Funktion bei Nebenstellenanlagen
      Synonyms: consultation call, call-back
            Note: private branch exchange function