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.