A system comprising processor means configured to collect and store data, display means controlled by the processor means, and switch means allowing the system to be set in a display mode or a data transfer mode. When the system is in the display mode the processor means is configured to control the display means to display stored data using user-readable numeric values, and when in data transfer mode the processor means is configured to generate a machine-readable-only visual representation of the stored data, and control the display means to display the machine-readable-only visual representation.