A runoff drain filter is comprised of a tray for being supported inside a runoff drain. In different levels of abstraction, a business operations model, an applications model, a physical requirements model and technical infrastructure model are produced. Alternatively, instead of the connection between the defective device and the common data line, the connection between a defective device and a common or an individual supply line is separated. The net effect is that a person can run with the pack, with heavy load, in rough terrain, with the pack staying relatively stable.