I would suggest the Ready Brake is the only true proportional system that I am aware of. Some systems provide braking force to the toad in proportion to the braking applied to the coach, but that is not necessarily what the toad requires. With the Ready Brake you have a positive feedback loop. The toad pushing on the coach results in increasing toad braking force until results are seen, then the braking force is decreased until the internal spring overcomes the pressure to the point the cable goes slack. This description might not make sense if you're not familiar with the operation of the system, but in simple terms, you get the required toad braking to relieve the force the toad is applying to the coach.