 Each JSF or TSF was divided into 4 two-stage grids.Early TNs had four JSF, for a total of 16 grids, 1024 J links and the same number of B links, with four B links from each Trunk Junctor grid to each Trunk Switch grid.Starting in the mid-1970s, larger offices had their B links wired differently, with only two B links from each Trunk Junctor Grid to each Trunk Switch Grid.