A side view of the inside of an HD frame is shown on the left side of Figure 1-8. A top-down  view of one row of an HD frame with cartridges in tier 0 (door side), 1 (Drive side), 2, 3, 4 and  5 is shown on the right side of Figure 1-8. Tier 5 is for LTO frames only. The IBM TS3500 storage-only frame, HD1 models S24 and S54, can be attached to the  TS4500 with the correct FC 1742 ordered. These generation 1 HD frames can be redeployed into a TS4500 if they are installed to the  right of the Lx5 frame. You must install FC 1742 before the frames can be added to a TS4500  library string. This feature code replaces the TS3500 cards to be supported on the TS4500,  as shown in Figure 1-9. The TS3500 tape library models S24 and S54 frames are high-density (HD) version 1  storage-only expansion frames, which were attached to TS3500 tape libraries and frames. Chapter 1. IBM TS4500 tape library  17 Figure 1-9 Changes to S24/S54 for TS4500 attachment Figure 1-8 The HD frame (left) and top-down view of a row in an HD frame (right) Models S24 and S54