I found a great article on www.etrailer.com here.
Trailer Brake Controllers
An electric trailer brake controller is a device that supplies power from a vehicle to a trailer's electric brakes. There are two types of electric brake controllers - Time Delay Activated ("solid state") and Proportional ("pendulum style"). Although the controllers' methods are different, both types of controllers are very similar. Both allow the user to adjust output or braking power. Both have a pressure sensitive manual override trigger that can be used to apply the trailer brakes independent of the vehicle brakes. Both have the same wiring configuration.
Time Delay Activated
Solid state controllers are "enabled" by the brake pedal switch and apply...
- Sticky