A brake controller is not needed with a trailer surge braking system unless using modern electric over hydraulic devices. The trailer in this case usually has either electric friction brakes or electric-hydraulic trailer brake actuators. Most basic brake controllers will generally have a +/- gain adjustment.
https://en.wikipedia.org/wiki/Trailer_brake_controller
BRAKE SYSTEM COMPONENTS. Boat Trailer Brakes & Utility Trailer Brakes. When selecting trailer brake components for your trailer, consider the weight of trailer fully loaded with all cargo and equipment. For multi-axle trailers, consider how many axles will be equipped with brakes to meet your stopping requirements.
http://www.easternmarine.com/em_store/trailerbrakes/
Trailer brake controller. A brake controller is usually an OEM or aftermarket installed device or module. It is mounted to the tow vehicle's driver's-side dashboard area, and engages a trailer’s electrical braking system either time delayed, or in proportion to the tow vehicle's brake engagement when slowing down or coming to a halt.
https://en.wikipedia.org/wiki/Trailer_brake_controller
Brakes - Air, Electric, Hydraulic. When selecting trailer brake components for your trailer, consider the weight of trailer fully loaded with all cargo and equipment. For multi-axle trailers, consider how many axles will be equipped with brakes to meet your stopping requirements.
http://www.easternmarine.com/em_store/trailerbrakes/
The brake controller is typically installed in the vehicle's driving compartment by running an electrical line from the trailer to the trailer wiring connector. Most require the user to adjust brake gain (braking intesnsity) to compensate for varying trailer load. If your vehicle came from the factory with a Class III or better towing hitch installed, chances are that it has a quick plug under the dash for a brake controller.
http://www.autozone.com/landing/page.jsp?name=trailer-guide-trailer-brakes
A surge brake system is entirely self-contained on the trailer and is activated when the towing vehicle decelerates. It operates very similar to your vehicles braking system. The momentum of the trailer pushes the surge brake housing forward acting like a foot on a brake pedal.
http://www.autozone.com/landing/page.jsp?name=trailer-guide-trailer-brakes
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http://www.ebay.com/sch/i.html?_nkw=trailer+brakes
Components of the electric/hydraulic system are mounted on the trailer and consist of an electric/hydraulic power unit, battery, hydraulic lines and hydraulic disc or drum brakes. A 12 volt power supply and electronic signal are supplied from the tow vehicle.
http://www.easternmarine.com/em_store/trailerbrakes/
Most recreational trailers use electric brakes; exceptions can include rental car-hauling trailers, which use surge brakes, and some large fifth wheels, which use air brakes. Most require the user to adjust the brake gain (braking intensity) to compensate for varying trailer loads.
http://www.autozone.com/landing/page.jsp?name=trailer-guide-trailer-brakes
Trailer brakes come in two basic varieties: electric and hydraulic. Electric trailer brakes are directly controlled by the brake pedal in your vehicle, and can be adjusted with an outboard unit mounted in the cab of your truck. Brake force is incrementally increased or decreased to achieve maximum braking power without locking up the trailer’s wheels when decelerating.
https://www.amazon.com/Automotive-Replacement-Brake-Trailer-Brakes/b?ie=UTF8&node=15722891
what are trailer brakes
Air, Electric and Hydraulic are trailer brakes. Trailer brakes are Air, Electric, and Hydraulic.   Air, Electric & Hydraulic are trailer brakes.