means that the BDF must be able to facilitate the teeing of the old and new switches to the building 33.8.1 Main Distribution Frame wiring, and facilitate the ready removal of the old PABX wiring without breaking service. Some of the more modern IDC connect The Main Distribution Frame (MDF) is located at the interface systems and frames tackle this need. between the external PTT cable and the PTT switching equipment. Its purpose is to provide the following: 33.9 Computer aided cable layout 1. Cross connection flexibility point. 2. Termination point for cable. Over the past two years the use of computers to assist in the design 3. Overvoltage protection. and management of cabling schemes has become commonplace. Computer aided cable layout 33/9 This application of technology has been brought about by two CAD and database technologies. In both systems the database is factors: used to store and maintain all relevant data on the cabling infrastruc- ture. This can be anything from a description of components to 1. The wider use of structured cabling schemes which provides costings and material lists which are generated automatically as the more flexibility than traditional cabling schemes. cables are routed on the floor plan. The CAD drawing is used to 2. The acceptance that buildings have to accommodate increasing represent the database information and to input data to the database technology. in a very fast and efficient manner. The CAD based system requires more training and will need more The main influence on this application of technology is the de- sophisticated equipment on which to run. However its greater ca- pendence that companies have placed upon it and the chaos that pacity to assimilate data makes it more productive than a database ensues when a change in the organisation occurs. Most office only system. workers today use a computer terminal, and the predictions are that by the middle of the decade every office-bound worker will have an 33.9.1 Using Computer Aided Cable Layout intelligent terminal on the