Complex sentence: In 1969, Xerox acquired Scientific Data Systems (SDS), which it renamed the Xerox Data Systems (XDS) division and which produced the Sigma line and its successor XDS 5xx series of mainframe computers in the 1960s and 1970s.
Split into simpler sentences: In 1969, Xerox acquired Scientific Data Systems (SDS). It renamed the division "Xerox Data Systems" (XDS) and produced the Sigma line and its successor the XDS 5xx series of mainframe computers in the 1960s and 1970s.