/COMMAND=command-character
Selects the command character. The command character is used to
access VT command mode by pressing Ctrl/command-character.
The command 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 disconnect character
(see the description of the /DISCONNECT=disconnect-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 command character is the "at" sign (@).