The Econet Eurocard is designed to fit in a standard Acorn system 2, 3 or 4 card frame. The interrupt line from the Eurocard must be connected to the NIRQ line on the 6502 CPU card, this wire should be linked across on side B of the connectors on the Acorn backplane to card slots that require it. This interrupt connection is normally on pin 28 B of the connectors. The card is enabled by address decoding on it into locations 1940 to 197F (hex) in the system memory map.