Additional Details ------------------------------ Product description: DUO is the next generation supplemental brake system. Introduced in 2003, the Stay-IN-Play experiences great reviews from customers and dealers alike. Dealers rave because of the ease of installation and the lack of returns from dissatisfied customers. Customers love it because it performs day in and day out. DUO takes the Stay-IN-Play to a new level. We call it DUO because two is better than one. First and foremost, DUO uses both air pressure and vacuum. Vacuum is created to energize the towed vehicle?s power brakes and the air pressure to apply them. Secondly, DUO requires two separate signals to activate the towed vehicle brakes. Using two activation signals is the best method for eliminating complicated electronics and control unwanted or unnecessary activation of the towed vehicle brakes. By combining the brake?s of the coach with deceleration, you have better control of the system rather than the system controlling you. We also believe that simplified electronics and fewer mechanical parts will provide you a better foundation and last longer. Another key difference in the DUO is the Coach Notification System. There is only one way to obtain reliable information about the towed vehicle?s brakes and we believe this to be through the towed-vehicle?s brake light switch. Many will argue that there is another way; that there is a better way, but if you think it through, you will agree, the brake light switch eliminates the question. One has to wonder, how many systems today are really easy to use? Many claims are made in advertising literature but is brand X really easy to use or do they just want you to think it is. DUO is REALLY easy to use, just turn it on. We make no inflated claims. You do have a two to three-hour install, just once. This is the DUO difference, install once and always ready. That is easy. Contact us with questions or to locate a dealer near you.