+@defun suspend-tty &optional tty
+If @var{tty} specifies a terminal device used by Emacs, this function
+relinquishes the device and restores it to its prior state. Frames
+that used the device continue to exist, but are not updated and Emacs
+doesn't read input from them. If @var{tty} is a frame, it means that
+frame's terminal; if it is @code{nil}, the function uses the selected
+frame's terminal. If @var{tty} is already suspended, the function
+does nothing.
+
+This function runs the hook @code{suspend-tty-functions} (each
+function gets one argument, the terminal that corresponds to
+@var{tty}).
+@end defun
+
+@defun resume-tty &optional tty
+Resume the previously suspended terminal device @var{tty}. If
+@var{tty} is a frame, it means resume that frame's terminal;
+@code{nil} means the selected frame.
+
+This function reopens the terminal device, re-initializes it, and
+redraws its with that terminal's selected frame. It then runs the
+hook @code{resume-tty-functions}, passing each function the terminal
+which corresponds to @var{tty}.
+
+If the same device is already used by another Emacs terminal, this
+function signals an error.
+@end defun
+
+@defun controlling-tty-p &optional terminal
+This function returns non-@code{nil} if @var{terminal} is the
+controlling terminal device of the Emacs session.
+@end defun
+
+@deffn Command suspend-frame
+This command @dfn{suspends} a frame. For GUI frames, it calls
+@code{iconify-frame} (@pxref{Visibility of Frames}); for text-only
+frames, it calls either @code{suspend-emacs} or @code{suspend-tty},
+depending on whether the frame is displayed on the controlling
+terminal device or not.
+@end deffn
+