Complex sentence: A telephone exchange is a telephone system located at service centers (central offices) responsible for a small geographic area that provided the switching or interconnection of two or more individual subscriber lines for calls made between them, rather than requiring direct lines between subscriber stations.
Split into simpler sentences: A telephone exchange is located at service centers (central offices) responsible for a small geographic area. In this area it provides the switching or interconnection of individual subscriber lines for calls made between them, rather than requiring direct lines between subscriber stations.