Traditional cantilever brakes used two cables, a main cable running down the centerline of the bike, and a second, "transverse" cable connecting the cantilever units on each side of the wheel. The main cable would pull upward on the middle of the transverse cable, causing the cantilever units to rotate inward.
The "direct pull" cantilever, also commonly known under its Shimano trademark name "V-Brake" is a simpler design, using only a single cable. The cable housing connects to one arm, and the inner cable runs across the top of the tire to the opposite arm. When the brake is applied, the housing pushes on one cantilever while the inner cable pulls the other.