For those who don't know, electric trailer brakes are drum brakes. The brake shoes are pushed out against the drum by the force of an electromagnet dragging on the smooth inner face of the drum and working a lever that pushes the shoes out. The trailer brake controller sends a pulse width modulated voltage to the brake magnets--it is 12 volts rapidly switched on & off...longer on and shorter off gives more magnetic force. Almost all trailer brakes need to be manually adjusted for wear. Some people have the mistaken idea that the correct way to descend a steep grade is to activate only the trailer brakes. The result is worn out trailer brakes. Another result is overheated and failed trailer brakes that do nothing to stop the rig.No lining left and magnets were finished.