A valve actuating system including a drive device having an axial extension, and having an actuator with an axial output side provided for coupling to a valve and with an opposing axial rear side, wherein the actuator has an attachment interface on the axial rear side thereof for the attachment of an auxiliary device interacting with the actuator, such as a display module, a control head, a position controller or a stroke-limiting module, wherein the attachment interface has a sectional surface onto which the auxiliary device can be tensioned by means of an axial locking device, wherein the axial locking device has a main body and a collar with a locking edge, with which at least one locking element is in contact on the side facing the actuator in order to tension the auxiliary device on the support surface, wherein the collar is formed by a retaining ring secured on the main body.