dweller - June 18, 2010 U.S. foghorns are increasingly becoming boater-activated. News story here... Tags General News and Events Turning the Horn Off Permalink Submitted by JensenNR on Tue, 08/10/2010 - 22:39. It is also possible to turn the U.S. automated horns off by keying the mic three times. This comes in handy, when someone decides to activate the horn in perfectly clear weather, just to show their friends that they can do it. Port Captain Niels R. Jensen, S/V Freelance Boater-activated foghorn keying Permalink Submitted by Adena-Marilyn on Sun, 06/20/2010 - 21:25. When you press your microphone button, the foghorn signal activation on Channel 79 requires a longer duration than 5 quick "dits" or "dots". Think of it as 5 "dahs" or "dashes".