ratio bringing the transmission to its highest gear u201c synchronous u201d refers in this context to a ratio of both variator and transmission at which a change from low to high regime produces no change in the transmission ratio so that at this ratio a smooth change can be made from one regime to the other the synchronous variator ratio constitutes a lower limit to the ratio range required of the variator in accordance with the present invention the transmission incorporates one way clutches which provide a limit on variator ratio specifically the illustrated embodiment has 1 a first one way clutch 22 in parallel with u2014 i e connected across u2014 the low regime clutch 18 and arranged to prevent the clutch 39 s input speed from exceeding its input speed and 2 a second one way clutch 24 in parallel with the high regime clutch 20 and arranged to prevent the clutch 39 s output speed from exceeding its input speed the concept of a one way clutch is well known to those skilled in the art it has first and second rotary shafts and permits relative rotation of the two shafts in one direction but not in the other one way clutches can be implemented using for example ratchet or sprag mechanisms a sprag type clutch is preferred for the present invention but other.