>> former white house staffers tell us the technical capability exists for the president to tape phone conversations. but that's different from a built in white house taping system. president kennedy used one as did president johnson. here trying to convince someone to be hayes campaign manager. >> any way you want to do it but i want you to do it. >> among nixon's legendary recording a 1972 oval office conversation on how to push back on the watergate investigation. >> what the hell did mitchell know about this thing. >> this one is often referred to as the smoking gun tape. >> that white house taping system was shut down in the summer of 197 at the height of the watergate scandal. >> the american people, press or the media didn't know anything about the taping systems. until alexander butterfield a white house aide in july of 1973 told the senate watergate committee -- told the staff that tlfrs a taping system.