R U=±U at+a0(0) R udt +U T=RC Z 2R RC T=T+T 1212 Z f T U R R U 1 =  (0) 1 0 o t uo = − ui dt +u   TL T UTH = −  ui dt +U 1 0 1 1  TH T UTL = −  ui dt +U 2 0 2 1  ui ui UZ RC   = − = − = 1 2 T f T T T RC R R T T f 1 2 1 2 1 1 2 = = + = = • 