VMS Help DECnet-Plus, DCL Commands, SET, HOST, /VTP, Qualifiers, /DISCONNECT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /DISCONNECT=disconnect-character

    Selects the disconnect character. The disconnect character is
    used to abnormally terminate VT association with the remote
    system by pressing Ctrl/disconnect-character.

    The disconnect character can be any ASCII character between @
    and z.  You cannot select a character currently defined as
    either the break character (see the description of the
    /BREAK=break-character qualifier) or the command character (see
    the description of the /COMMAND=command-character qualifier).

    The ASCII characters between @ and z include the alphabetic
    characters in both upper and lower cases, the "at" sign (@),
    the backslash (\), the right bracket (]), the circumflex (^),
    the underscore (_), and the grave accent (`).

    By default, the disconnect character is the "backslash" (\).