A turning knob with a lock for an electric circuit indicating a body for receiving a barrel rotating relative to a stator. The barrel includes springs receiving a key configured while rotating to take up at least two functional retained or released positions and having at one of its ends a shank configured to be actuated by rotating the key. The body has an inner cylindrical sleeve whereon the stator is urged to be positioned, the inner sleeve having a number of identical members for positioning the stator, each positioning member of the inner sleeve matching a corresponding positioning member of the stator, so as to select the position of the stator relative to the body.