TRAILER COUPLING

In order to comprehensively provide, with a trailer coupling, a ball neck carrying a coupling ball as well as a socket receptacle for a plug to supply power to units acting on the coupling ball, wherein the socket has a socket housing with a housing sleeve that is provided with a plug-in opening, and wherein the plug-in opening can be closed by a cover pivotally mounted on the housing sleeve, the problem of being able to mount the sockets as inexpensively and simply as possible is solved by the proposal that the socket receptacle has a receiving channel, wherein a sensor is provided in the ball neck or in the coupling ball and a receiving channel of the socket receptacle for the housing sleeve has a recess for receiving a sensor connection line.