Shares of Newmark Security plummeted after it said first half pre-tax profit more than halved but it remains optimistic for a better second half.The electronic and physical security systems provider posted a pre-tax profit of £360,000 in the six months ended 31 October 2010 from £883,000 the same time a year earlier. Revenue fell 13% to £6.1m.Chairman Maurice Dwek said, "Trading in the current environment continues to be difficult but the Board anticipates an easing of current market constraints resulting in a more positive second half of the financial year."Newmark said delays in customers placing orders has continued.However in the longer term Newmark expects new geographical markets and its portfolio of products to produce valuable revenue streams going forward.