By David Russell, reporter at OptionMonster NEW YORK -- OptionMONSTER's Heat Seeker tracking systems detected the purchase of some 8,000 September 42 calls, most of which priced for $1.02 to $1.12. Previous open interest was just 509 contracts at the strike, so new money was clearly being put to work. Calls lock in the price where stock can be purchased no matter how far it might climb. Leverage from these options can allow investors to turn small stock moves into big winners. Xilinx ( XLNX) shares rose 2.52% to $41.16 yesterday and are up 27% in the last year. The September 42 calls, meanwhile, appreciated more than 10% to $1.26 by yesterday's close. The company beat expectations in its last two earnings releases, and the next quarterly report is scheduled for July 17. Its shares are parked at the same price level where they peaked in 2001 and 2004, which could make some traders expect a big rally if they break out. Owning calls lets them position for such a move with much less risk than owning the shares directly. Overall calls in the name outnumbered puts by more than 10 to 1, reflecting the session's bullish bias. More than 12,700 contracts traded in all, compared with average volume of just 2,430. Russell has no positions in XLNX.