Samsung Techwin, Samsung Group\'s defense and machinery unit, said Thursday that it posted an operating loss in the fourth quarter of 2011 due to lower operating margin. The company logged an operating loss of 2.68 billion won (2.35 million U.S. dollars) in the fourth quarter, turning into the red from an operating profit of 34.75 billion won tallied in the previous quarter, according to a regulatory filing. Sales gained 9.39 percent on-year to 819.22 billion won during the October-December period, but net profit plunged 77.31 percent to 14.37 billion won over the cited period. \"The company\'s earnings results fell below our estimates and market consensus. This weak result was mainly attributable to a plunge in semiconductor equipment and component sales. Moreover, defense and CCTV sales were weaker than expected,\" said Park Won- jae, an analyst at Daewoo Securities.