BC ▁on ▁August ▁ 7 . ▁An ▁estimated ▁ 8 5 % ▁of ▁Americans ▁with ▁television ▁sets ▁tun ed ▁into ▁at ▁least ▁one ▁portion ▁of ▁the ▁hear ings . ▁ ▁On ▁Friday , ▁July ▁ 1 3 , ▁ 1 9 7 3 , ▁during ▁a ▁pre lim inary ▁interview , ▁deput y ▁minor ity ▁coun sel ▁Donald ▁Sand ers ▁asked ▁White ▁House ▁assistant ▁Alexander ▁But ter field ▁if ▁there ▁was ▁any ▁type ▁of ▁recording ▁system ▁in ▁the ▁White ▁House . ▁But ter field ▁said ▁he ▁was ▁rel uct ant ▁to ▁answer , ▁but ▁finally ▁admitted ▁there ▁was ▁a ▁new ▁system ▁in ▁the ▁White ▁House ▁that ▁automatically ▁recorded ▁everything ▁in ▁the ▁O val ▁Office , ▁the ▁Cab inet ▁Room ▁and ▁others , ▁as ▁well ▁as ▁N ixon ' s ▁private ▁office ▁in ▁the ▁Old ▁Executive ▁Office ▁Building . ▁ ▁On ▁Monday , ▁July ▁ 1 6 , ▁ 1 9 7 3 , ▁in ▁front ▁of ▁a ▁live , ▁tele vised ▁audience , ▁chief ▁minor ity ▁coun sel ▁Fred ▁Thompson ▁asked ▁But ter field ▁whether ▁he ▁was ▁" aware ▁of ▁the ▁installation ▁of ▁any ▁listening ▁devices ▁in ▁the ▁O val ▁Office ▁of ▁the ▁President ". ▁But ter field ' s ▁revel ation ▁of ▁the ▁tap ing ▁system ▁transformed ▁the ▁Water gate ▁investigation . ▁C ox ▁immediately ▁sub po ena ed ▁the ▁t apes , ▁as ▁did ▁the ▁Senate , ▁but ▁N ixon ▁refused ▁to ▁release ▁them , ▁cit ing ▁his ▁executive ▁privile ge ▁as ▁president , ▁and ▁ordered ▁C ox ▁to ▁drop ▁his