An exemplary field device connection unit includes a base plate on which a plurality of connection elements for connection of connecting lines with field devices and a plurality of module slots for receiving in each case one plug-in unit of different plug-in unit types. To avoid erroneous configurations, an identical type coding is assigned to the plug-in units of the same plug-in unit type, which identical type coding is formed by a plurality of wedge-shaped code elements which are anchored rigidly in the plug-in unit, and a plurality of wedge-shaped code elements are assigned to each module slot, which wedge-shaped code elements are mounted moveably about a rotary spindle between two opposite stops and whose wedge tips are oriented, in an initial rest position, centrally between the stops.