VMS Help LOGOUT, Qualifiers, /HANGUP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /HANGUP
       /NOHANGUP

    Determines, for dialup terminals, whether the phone hangs up
    whenever you log out. By default, the setting of the /HANGUP
    qualifier for your terminal port determines whether the line
    is disconnected. Your system manager determines whether you are
    permitted to use this qualifier.