Connection device

A plug-in connection device for the self-actuating electrical connection of a motor vehicle trailer to a towing motor vehicle with a socket (D) and a plug (S), which can be disposed on the motor vehicle trailer (for example the plug S) or the towing motor vehicle (for example socket D) During the coupling of the motor vehicle trailer to the towing motor vehicle, socket (D) and plug (S) can be aligned with respect to one another and can be moved by means of a drive (10), developed for example as a piston-cylinder configuration, relative to one another between an advanced connection position and a retracted resting position. Preferably a cover (5) of the socket (D) can be opened by displacing the contact insert (1), bearing contact sleeves (11, 12), in the direction of the connection position with the aid of drive (10). When the contact insert (1) is retracted into the resting position, the cover can be closed again. The plug (S) is supported such that it is resiliently yielding laterally against the action of a retaining spring (213).