While commuter bicycles can generally get by with a rear-wheel-only coaster brake, mountain and cyclocross bikes require both front and rear brakes - along with the hand levers used to activate them. Although this doesn't pose much of a challenge for most riders, it does for those who only have the use of one hand. One possible solution is to use a system that joins both brake cables to one common end, which then goes into a conventional lever. Another solution, however, is to use Paul Component Engineering's dual-cable Duplex lever.
The Duplex was originally designed for bicycle polo players, who needed to keep one hand free for swinging their mallets. It's basically just one brake lever, with two cable inputs. Individual barrel adjusters allow riders to adjust the reach of each brake, so they can either engage simultaneously, or one a little before the other. Ideally, it would be nice for riders to be able to modulate between front and rear as each situation dictates, but it's hard to picture how that could be done using just one lever.
The aluminum lever's choice of two pivot points lends it to use with short- or long-pull rim brakes of almost every style. It will also work with mechanical disc brakes, but not with hydraulics. As is the case with regular levers, a reach adjust screw determines how far the lever sits from the handlebar, to accommodate different-sized hands.
Another nice feature of the lever is the fact that it is completely symmetrical, so it can be used on either the left or right side of the handlebar. The few similar products in the marketplace, such as the Pyramid dual lever, must be purchased side-specific.
The Paul Duplex lever weighs 94 grams (3.3 oz), comes in anodized black or silver, and is available online for US$63.