Reports in the British press say Twin Cities based Control Data Systems is being sold to British Telecommunications, Britain's largest telephone company. There has been no official confirmation of the buyout. But an announcement is expected at a news conference scheduled for this afternoon in Minneapolis . Control Data Systems is the smaller of two companies resulting from the split of the original Control Data corporation in 1992. The old firm was a world leader in the manufacture of mainframe computers and was central to Minnesota's evolution as a center of high technology.