A trailer brake controller and system detects absolute deceleration of a trailer by incorporating an electronic gyroscope/accelerometer combination in order to accurately calculate the deceleration subtracting out the component which is due to the force of gravity. The controller and system also receives and reads information from the towing vehicle's speed sensor. The system detects the deceleration of the trailer and sends a signal to a trailer brake activation circuit based upon an acceleration status of the trailer. In some embodiments, the system detects that the trailer is decelerating and the trailer control device sends a signal to the trailer braking system activation circuit to activate the trailer brakes. Particularly, the system is able to detect that the trailer is decelerating at an unsafe rate and to activate the trailer brakes and slow the trailer to a safe speed.