CS1 is what was previously understood as Horizontal cabling, where one end of the link is terminated at an Equipment Outlet (EO), and the other end is terminated into any one of the types of Distributors (A, B, or C).
In this example, there are 10 CS1 horizontal links, some going directly to an Equipment outlet and some passing through consolidation points to an Equipment outlet. These CS1 horizontal links are shown here as red dotted lines.