VMS Help DTM, DEFINE, /KEY, Command Qualifiers, /ECHO  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   /ECHO (D)
   /NOECHO

   Specifies whether the command is displayed on your screen after
   you press the defined key. You cannot specify both the /NOECHO
   qualifier and the /NOTERMINATE qualifier.