control-S vi. "Stop talking for a second." From the
ASCII DC3 or XOFF character (the pronunciation /X-of/ is
therefore also used). Control-S differs from {control-O} in
that the person is asked to stop talking (perhaps because you are
on the phone) but will be allowed to continue when you're ready to
listen to him -- as opposed to control-O, which has more of the
meaning of "Shut up." Considered silly.