(Reuters) – British telecoms testing company Spirent Communications Plc estimates full-year revenue to fall about 14 percent due to lower-than-expected demand from the United States in the fourth quarter. Spirent Communications also estimates fourth-quarter revenue of about $115.0 million, at the lower end of its forecast. The London-listed company had cut its fourth-quarter revenue forecast in October due to a delay in customers taking delivery of its products. Spirent Communications also said it was looking at selective acquisitions to allow the company to return to growth.