Patent ID: 8724333

Claim:
Hardware unit, comprising an electrical field device and an expansion module, wherein the electrical field device has a housing with an opening formed on one side thereof, at least one input, at least one output, and an electronic circuit which has a microcontroller, a memory and a circuit board, and wherein the expansion module has a housing and an electronic circuit with a circuit board, wherein the circuit board of the expansion module has mating contacts on an end for making electrical contact with contacts which are connected to the circuit board of the electrical field device, the contacts which are connected to the circuit board of the electrical field device being accessible from outside of the housing, and wherein an open recess is formed in the circuit board of the electrical field device into which the expansion module is inserted via the opening of the housing of the field device in a manner such that the expansion module does not have any conductive contact with the field device except in the region of the mating contacts due to the open recess in the circuit board of the field device being larger than the expansion module except within a region at which the contacts that are connected to the circuit board of the electrical field device are located.