fire safety curtain making the fire curtain heavier than the counterweight supporting the fire curtain and the fire curtain descends. Resetting an overbalance bar with the chain type of release also requires at least two people. (Note: it's smart to mark the links that hook onto the trip levers before you test the system. This will take the guesswork out of resetting the chains.) The first thing to do is to reset the release line. If manually released, the end of the fire curtain release line must be retrieved and reattached to the release station. If a fusible link has separated it must be replaced before the fire safety curtain can be reset. The next step is for two people to go the grid and pull the overbalance bar off of the top of the fire curtain by pulling up on the chains attached to the overbalance bar. Replace the marked links onto the trip lever hooks. (If the chains are not marked raise the bar so that it is approximately three feet above the level of the fire curtain when it is in its storage position.) The third step is to raise the fire safety curtain to its storage position above the proscenium opening. Resetting the type of overbalance bar which is suspended by the release line is a little easier. In this version there are two pulleys attached to the overbalance bar and the release line drops from the grid through pulleys attached to the overbalance bar and then back up to the grid. When the fire line is released, the end of the release line travels twice the distance that the overbalance bar travels. This version is often used when there is no walking grid available, as it is possible to reset from the floor. (When testing any overbalance system it is a good idea to first attach a piece of tie line to the end of the fire line. The length of the tie line should be at least two and a half times the distance that the fire safety curtain will travel. This will simplify retrieving the end of the fire line after the test.) Overbalance Arbors A modern version of the overbalance system uses a separate overbalance arbor and guide system (figures 7, 8, and 9). Located in this guide system are two arbors, an upper and a lower. A cable is attached to the lower overbalance arbor and goes up and over a loft block, then over the head block, and is attached to the fire curtain counterweight arbor. The upper arbor contains the overbalance weights and is held off of the lower arbor by the fire curtain release line. When the fire curtain release line is released the upper counterweight arbor drops onto the lower counterweight arbor adding weight to the fire curtain side of the balance beam. The fire curtain then Figure 5. Detail of chain tethers. Figure 6. Detail of trip levers. TD & T F A L L 2 0 0 5 23