The present invention relates to an active plug-in function unit, intended for plugging into a multipolar plug contact device on a circuit board or back plane, and comprises a base plate, a connector, an electronic circuit and a cover. According to the invention, the connector is a module-type multipolar sleeve connector (3) mounted on one end of the base plate (2), the base plate extending in the direction of the sleeve connectors. The electronic circuit (4) is mounted on the base plate (2) and connected to the sleeve connectors. The cover (5) is preferably made of metal and is placed over the electronic circuit (4) and, together with the base plate (2) and the sleeve connector (3), forms an EMC-casing around the circuit. The dimensions of the function unit are such that its projection, when plugged into the circuit board (A) or the back plane (B), falls within the dimensions of the plug contact device (C).