A linear actuator system with a controller, said controller comprising a controller and programmable means for controlling the operation of an electrical motor. The electrical linear actuator system comprises a user control unit (1), an electrical cord with a plug for connecting the user control unit (1) and the controller, where the controller and/or the user control unit comprises a socket (1a) for receiving the plug (2). The plug (2) comprises a locking ring (5), which is rotatable relative to the plug (2), and the socket (1 a) comprises an opening (16) for receiving the plug (2) including the locking ring (5) in the opening (16) of the socket (1 a). The socket (1 a) further comprises an aperture (4) through which a part of the locking ring (5) is accessible when the plug (2) including the locking ring (5) is inserted into the opening (16) of the socket (1a). The locking ring (5) and the opening (16) of the socket are adapted such that the locking ring (5), when inserted in the opening (16), can be rotated between an unlocked position and a locked position: where, in the unlocked position, a protrusion (8a, 8b) is received in and aligned with an axial part (12a, 12b) of a recess (12), such that the plug (2) may freely be inserted into or removed from the socket (1a), and where, in the locked position, the protrusion (8a, 8b) engages the radial part (12c,12d) of the recess (12), such that the plug (2) is prevented from being unplugged.