Air Force One is the only air brake system that energizes the towed vehicle's power brakes through a patent-pending process that does not require an electronic vacuum pump. In fact, Air Force One has no moving parts to wear out at all. Air Force One is also the industry's first and only supplemental brake system that protects the coach with a patent-pending breakaway system that seals the coach's air supply in the event of a separation of the coach and the towed vehicle. SMI braking systems are truely unique. Both systems utilize the towed vehicle's power brakes, allowing for soft, effective braking. With the use of Dual-Signal Activation, the Stay-in-Play DUO braking system CANNOT activate when you don't want it to, even down a grade; and with the Air Force One, you get true mirrored braking. The movement of the coach's brake pedal is identically reproduced in the towed vehicle; progressive and directly proportionate braking effort. Best of all, it's all automatic! Both models include coach notification, so you always know exactly how and when your brake is performing. The innovative design of the Air Force One Brake System allows the operating unit to be installed under the hood of the towed vehicle. Air pressure from the coach is used to create vacuum for the towed vehicle's power brakes, therefore, Air Force One requires no moving parts. With no moving parts, there is nothing to wear out and nothing to adjust, ever. Through an exclusive, patented process, Air Force One creates vacuum from air pressure. The towed vehicle's power brakes are active without the engine running. Using the power brakes creates a soft brake pedal that requires sustantially less force in the towed vehicle. In addition, since Air FGorce one uses air pressure to creat vacuum, there is no battery drain on the towed vehicle. Using the coach air-brake supply is the only way to create 100% true proportionate and progressive brake effort - the harder you apply the coach brake, the harder the towed-vehicle brakes are applied. Best of all, Air Force One Brake Systems do it automatically.