Demco Stay-In-Play DUO combines the power of air pressure and the gentleness of vacuum to give you the fastest most powerful self-contained supplemental brake ever. DUO uses the power and speed of air pressure to activate your towed vehicle brake pedal while creating vacuum for the power brake system. These two features combine to create the only progressive and proportionate vacuum-assisted system with total control. DUO requires both deceleration and coach brake lights to apply the towed vehicle brakes. By combining two separate signals the need for complicated electronics is eliminated, which provides you a more reliable, long-lasting system. In addition, DUO is a pioneer in user-friendly operation â "Just turn it on and tow." DUO does not have to be taken in and out for normal operation of the towed vehicle. Unhook the car and drive off, that's all. No box, no wires, in fact no physical connection to the motorhome at all.• Patent-pending air cylinder applies your towed vehicle's power-assisted brakes and automatically applies proportionate and progressive brake effort• Only 10 pounds of force on your brake pedal in normal braking• "Panic Stop Braking" with up to 3 times additional stopping effort in a panic• Coach notification of brakes applied with every unit• Creates vacuum to provide totally reliable and consistent brake application• No unwanted or unnecessary brake activations on grades or over bumps• "Zero" setup for towing• Simple installation mounts the small operating unit under the hood of the towed vehicle• The air cylinder is so small it fits in the palm of your hand• On/off operation means you are tow ready in less time Only 10 lbs. of force is need on your brake pedal in normal braking Panic Stop Braking provides up to 3 times additional stopping effort User-friendly, ""turn it on & tow"" operation | Demco Stay-In-Play DUO Flat Tow Brake System With Wireless Coachlink Monitor for Hydraulic Brakes