An apparatus is described that receives a brake control signal from the brake controller of a tow vehicle, and displays characteristics of that brake control signal including commanded brake force. The apparatus includes a data processor, brake simulation circuitry, brake integration circuitry, and display circuitry. The brake simulation circuitry sequentially applies several parallel resistors to the brake control signal in response to commands received from the data processor. These parallel resistors cause the load current on the brake controller to ramp up, mimicking the electrical signature of electric trailer brakes. At the same time, the brake integration circuitry integrates the brake control signal. Lastly, the display circuitry displays an indication of a value of the integrated brake control signal.