The Model 10 Brake Test Instrument (BTI) is a servo-controlled, electro-hydraulic device, designed and built by the General Motors Proving Ground. It is designed to apply a controlled force to the car brake pedal. Thus, car braking systems can be evaluated under repeatable pedal applications.The Brake Test Instrument is capable of controlling brake pedal force in any one of four different modes: Mode 1 It will apply any pedal force selected within the range of 0 to 300 lbs. Mode 2 It will continuously modulate or vary the pedal force to maintain any selected vehicle deceleration up to wheel slide. Mode 3 It will apply pedal force at any selected apply rate within the range of 0 to 50 lb./sec. Mode 4 It will continuously modulate, or vary, the pedal force to maintain any selected line pressure in the brake system. For any of these four selected force modes, the BTI can measure and plot any two of the following transducer signals versus a third on its flat bed two-pen recorder: (a) Pedal Force, (b) Pedal Travel, (c) Deceleration, (d) Time, (e) Brake line pressure or any other externally sensed signal.The BTI is also capable of switching from one force mode to another whenever a preselected value is reached. For example, it will operate in the constant deceleration mode until some selected pedal force is reached - say 100 lbs. When pedal force reaches 100 lbs., it then automatically switches to constant force mode and holds this 100 lbs. for the rest of the brake stop.