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.