I got a trailer used about a year ago. It has brakes on the back axle but no control box on the trailer, just wires that run to the front of the trailer from the brakes. I would have thought it would have come with the control box from the factory if it was needed. Maybe im wrong.

 

Trailer brakes come in several varieties. Hydraulic, air and electric
Hydraulic are a stand alone system with either an electric over hydraulic actuator or a surge type actuator. Air brakes are driven off the tow vehicle. Electric brakes are also driven off the tow vehicle with an electric trailer brake controller.

There is no need for a brake control box for electric brakes "on the trailer." It should be in your tow vehicle where you can activate and adjust it while driving. There are many types of electric brake controllers ranging in price from $35 to about $200. The most popular and the number one selling controller in the country is a Tekonsha Prodigy, recently replaced by the Tekonsha Prodigy P2. I recommend if you are towing this trailer you look into getting a Prodigy.... particularly since it only has 1/2 of the brakes that are required by the DOT. Many stated do not enforce trailer brake requirement laws, but some have harsh penalties for not having brakes on all axles.