This paper questions how we could and should present diagrams to blind people using computer-generated sound. Using systems that present information about one part of the diagram at a time, rather than the whole, leads to two problems. The first problem is how to present information so that users can integrate the information into a coherent overall picture. The second is how to select the area to be presented. This is looked at by using a system that presents graphs representing central heating system schematics. The system presents information by user choice through either a hierarchical split of information and navigation system, or a connection oriented split of information and navigation system. Further, we have a split as to whether a simple system of presenting location of nodes is used, or not. Tasks, classified as being based on hierarchical information or connection-based information, were set using the system and the effect of the different models was recorded. It was found that there was a match of task to navigation system, but that presentation of position had no discernable effect.