Radisys ( RSYS) posted a strong third quarter but guided lower for the fourth quarter and expanded its stock buyback. The Hillsboro, Ore., tech outfit made $5.9 million, or 25 cents a share, for the quarter ended Sept. 30, up from the year-ago $3.8 million, or 17 cents a share. Revenue rose to $74.9 million from $61.7 million a year earlier. Wall Street analysts had been looking for a 19-cent-a-share profit on sales of $73.8 million. But the company said fourth-quarter numbers won't be as strong. Radisys, which describes itself as a supplier of advanced embedded systems, said it expects to make 13 cents a share, flat with a year ago, on revenue of $70 million. Analysts surveyed by Thomson First Call had been looking for a 21-cent-a-share profit on sales of $76.8 million. Radisys says it expects to boost research-and-development spending by $1 million in the quarter. Radisys also said it would buy back as much as $25 million worth of stock, up from $5 million. Its shares were halted late Thursday after falling 34 cents to $17.65 in regular trading.