A connector comprising: a body for plugging in or on the body of a complementary connector along a plugging axis X-X′; connection means for co-operating with complementary connection means of the complementary connector so as to connect together electrical or optical conductors; and a locking sleeve that surrounds the body of the connector and that is adapted to co-operate with the body of the connector and with locking means provided by the complementary connector in such a manner as to block relative movement between the connector and the complementary connector in the plugging direction, the locking sleeve being movable in rotation about the axis relative to the body of the connector between an unlocking position in which the connectors can be separated and a locking position in which the connectors cannot be separated; wherein the connector includes a brake ring that co-operates with the body of the connector by being movable at least in rotation about the axis between a braking position in which the ring opposes any turning of the locking sleeve and a disengaged position in which the ring does not oppose any turning of the locking sleeve.