The invention concerns a turning knob (1, 1') with lock for an electric circuit comprising a body (10) for receiving a barrel (11) rotating relative to a stator (14), said barrel (11) comprising springs (110), receiving a key (2) capable while rotating of taking up at least two functional retained or released positions and having at one of its ends a shank (11d) capable of being actuated by rotating the key. Said knob (1, 1') is characterized in that the body (10) has an inner cylindrical sleeve (102) whereon the stator (14) is urged to be positioned, said inner sleeve having a number of identical members for positioning the stator, each positioning member of the inner sleeve (102) matching a corresponding positioning member of the stator (14), so as to select the position of the stator (14) relative to the body (10).