Pendulum Style Controllers are "enabled" by the brake pedal switch and "activated" by a Pendulum Circuit that senses the vehicle's stopping motion and applies appropriate voltage to the trailer's brakes. Once properly adjusted, the trailer will slow down at the same rate as the tow vehicle. This increases braking efficiency and cuts down on break wear and tear. Pendulum style controllers break smoothly and function well in bad braking conditions. On the downside, with few exceptions, inertia-activated controllers are bulky, tend to cost more, and need to be mounted and calibrated on the level.