Abstract: A brake controller system includes a trailer mounted brake controller and a towing vehicle mounted brake controller, where the controllers exchange signals and data via a communication network so that braking actions of each of the trailer and the towing vehicle can be coordinated based on current driving statuses of the other, and where the trailer mounted brake controller includes a first interface receiving trailer status signals from sensors of the trailer; a second interface for receiving towing vehicle status signals, relating to a status of the towing vehicle and/or its mounted controller, from sensors and/or controllers in the towing vehicle; a third interface for transmitting brake control signals to brakes of the trailer; and a signal processor for generating the brake control signals based on the trailer and towing vehicle status signals.

Abstract: A decrease in a terminal voltage of a battery is suppressed in a vehicle control device having a function of driving a pump motor to operate an automatic brake, and a function of driving an EPB motor to operate an EPB. When a brake ECU receives an EPB request during the operation of the automatic brake, and an elapsed period after a start of the automatic brake becomes more than a first set period t1, the brake ECU starts the EPB motors. Moreover, when the brake ECU receives an automatic brake request during the operation of the EPB, and an elapsed period after a start of the EPB is not more than a second set period t2, the brake ECU suspends the operation of the EPB, and starts the automatic brake.

Abstract: In a method for setting a parking brake that has an electromechanical brake device having an electrical brake motor, the release time duration for displacing the electrical brake motor in the release direction is determined from the closing time duration in which the brake motor was previously displaced in the closing direction.

Abstract: A vehicle comprises a speed-sensing device outputting a signal indicating a velocity of the vehicle, a brake system outputting a signal for indicating when the brake system is being commanded to a brake torque providing state, and a trailer brake controller coupled to the speed-sensing device and the brake system. The trailer brake controller utilizes the signal of the speed-sensing device to determine when the vehicle is in a zero-velocity state and utilizes the signal of the brake system to determine when the brake system is being commanded to the brake torque providing state. The trailer brake controller transitions a brake-actuating output signal thereof from a speed-dependent zero-velocity output signal value to a trailer hold zero-velocity output signal value greater than the speed-dependent zero-velocity output signal value when it is determined that the brake system is in the brake torque providing state while the vehicle is in the zero-velocity state.

Abstract: An electronic drive includes an electro-mechanical brake associated with a direct-current motor. A first valve or diode connects one of the terminals of the direct-current motor with the first electrical terminal of the brake in a forward direction. A second valve or diode connects the other terminal of the direct-current motor with the first electrical terminal of the brake. A second electrical terminal of the brake is at least indirectly connected with a reference voltage.

Abstract: Towed vehicles can be extremely heavy. Accordingly, it is too much of a burden to the braking system of a towing vehicle to not have brakes on the towed vehicle. Controlling the brakes of the towed vehicle must be accurately applied otherwise very dangerous conditions can be created. A method of controlling braking of a towed vehicle is, therefore, needed. The method comprises receiving speed signals based on speed of a towing vehicle, or a towed vehicle, or both said towing vehicle and said towed vehicle, receiving pressure signals based on pressure of a hydraulic brake system of the towing vehicle, and generating a brake output signal based on the speed signals and the pressure signals.

Abstract: A vehicle braking force control device which, at a normal time, performs antilock brake control when the slip ratio of a wheel has become equal to or greater than a predetermined threshold. The control device acquires from the engine control unit an accelerator pedal position signal corresponding to an accelerator pedal position, a clutch connection signal corresponding to a state of connection of a clutch, and a power transmission signal corresponding to a state of power transmission of a transmission. When engine braking is large on the basis of the accelerator pedal position signal, the clutch connection signal, and the power transmission signal, the vehicle braking force control device changes the predetermined threshold value to an offset threshold value that makes it harder to perform the antilock brake control than at the normal time.

Abstract: A control device for a vehicle includes: a charge control portion that adjusts an upper limit of charging power to a battery to prevent a negative electrode potential of the battery from dropping to a lithium reference potential, based on a charge/discharge history of the battery; a braking control portion that detects a sharing ratio between hydraulic braking force by a braking device and regenerative braking force for desired braking force according to a brake pedal depression amount so that a motor generator generates a regenerative braking force within a range of the adjusted upper limit of charging power; and a setting portion that variably sets, according to the hydraulic response rate detected by the detection portion, a degree of limitation of the upper limit when restricting charging current to the battery by restricting the upper limit.

Abstract: An improved braking system and brake control method for a vehicle, in particular a truck, utilizes at least one pressure line for carrying a medium from at least one pressurized medium source to a brake device, and a brake pedal for receiving brake commands from a vehicle driver and for operating a brake line, which can be connected to the brake device. A pilot control valve with accompanying measuring capability quantitatively determines the brake pressure demanded by the vehicle driver.

Abstract: Reverse proximity sensors are used to determine an angle between a towed trailer and the towing vehicle. The trailer sway control determines a trailer angle of sway based upon proximity sensor readings from the reverse proximity sensors and from a sensor reading of an angle of turn of a steering wheel of the towing vehicle. Provided the determined trailer angle of sway exceeds a range that can be tolerated, a controller sends instructions to apply necessary braking to the vehicle or trailer to mitigate the trailer sway.

Abstract: An electric braking apparatus which first moves a piston in a detaching direction or passes a current to move the piston in the detaching direction in order to detect a pad contacting position. Furthermore, while the piston moves in the detaching direction, pad non-contact judgment is performed. After a pad non-contact state is confirmed, the piston is moved in a pressing direction to detect the pad contacting position. When the piston does not move in the detaching direction, it is judged that a parking brake has an ON-state, and it is waited until a host system instructs parking brake release.

Abstract: An electromechanical parking brake system for a heavy vehicle braked by air-actuated service brakes includes an EPB-ECU and a first electromechanical parking brake actuator controlled by the EPB-ECU. The electromechanical parking brake system further includes a redundant sub-system for applying a second parking brake in an event of a failure in the EPB-ECU or the first electromechanical parking brake actuator.

Abstract: A commercial vehicle trailer includes an electronically controlled braking system having an electronic control unit that has a parameter memory having one or more memory areas that can store vehicle-specific data. The electronic control unit controls the electronically controlled braking system based on the vehicle-specific data, and has an interface to an external computer. To permit reliable correlation of the vehicle-specific data to the commercial vehicle trailer, information is displayed on the trailer itself that characterizes the vehicle-specific data and that can be read into the computer via a reader unit. Based on such information, the appropriate vehicle-specific data is transferred to the electronic control unit.

Abstract: A drive system is provided for a utility vehicle and includes an alternating-current (AC) motor for providing a drive torque. An AC motor controller receives a battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, forward/neutral/reverse (FNR) signal, and run/tow signal indicative of the utility vehicle being configured to be driven and being configured to be towed. The AC motor controller generates an AC drive signal for the AC motor, wherein the AC drive signal is based on the battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, FNR signal, and run/tow signal.

Abstract: Apparatus and method for detecting the connection of a trailer to a vehicle. The apparatus is connected to a pneumatic pressure line of the trailer's service braking system, and measures the pressure of the system to determine if the trailer is properly connected to the vehicle when the vehicle's engine is running. Further, the apparatus also contains an algorithm that monitors the signals from other vehicle systems, and uses that information to determine the trailer characteristics. The vehicle engine control system receives information from the apparatus and adjusts the various vehicle systems accordingly.

Abstract: When swaying motions of a trailer or semi-trailer of a car-trailer combination are encountered, input signals which are taken into consideration to calculate a reference signal frequently include also oscillation components, due to which driving dynamics control for stabilization of the car-trailer combination can become very unreliable. To enhance the reliability of driving dynamics control of this type, a method is disclosed in which an input signal (Y) is sensed that includes signal oscillations which are due to a swaying motion of the trailer or semi-trailer and are superimposed on a base component (YBasis) of the input signal (Y). A reference signal is calculated from the input signal (Y), in which case the calculation is executed in such a way that the reference signal by approximation corresponds to a reference signal which is determined from the base component (YBasis) of the input signal (Y).

Abstract: The present locomotive brake control system includes a vacuum relay valve responsive to air brake apply and release signals on the air brake pipe to provide vacuum brake apply and release signals on a vacuum brake pipe. A locomotive brake controller is responsive to the brake apply and release signals on the air brake pipe to control the brake cylinder to apply and release the locomotive brakes in an air mode, and is responsive to the brake apply and release signals on the vacuum brake pipe sensed by a transducer to control the brake cylinder to apply and release the locomotive brakes in a vacuum mode.

Abstract: The invention provides an electro-mechanical brake system which can keep a stop state even if a malfunction is generated in a parking brake, and an electro-mechanical brake apparatus used for the electro-mechanical brake system. An electro-mechanical brake actuator presses a brake pad to a disc rotor so as to independently brake a braking force of each of wheels. A parking brake is constituted by a pawl portion attached to a motor of a motor driving the electro-mechanical actuator and a latch. A main controller detects a failure of the parking brake on the basis of a motor displacement at a time of reducing a motor current, and increases the pressing force in the remaining normal parking brake in the case that the parking brake failure in one wheel or more is detected.

Abstract: A system for providing enhanced force and motion stability and management for a tow-vehicle towing a trailer assembly is disclosed. The system includes a tow-vehicle with an electronic stability enhancing system in communication with a processor with memory, and sensors located on the tow-vehicle are used for detecting engagement with a trailer and communicating with a trailer electrical system and the processor. Computer instructions instruct the processor to identify specifications representing the tow-vehicle and the trailer and to calculate at least one force, at least one motion, and combinations thereof, affecting the tow-vehicle and trailer assembly. Computer instructions provide instructions for braking to at least one wheel of the tow-vehicle using the at least one force, the at least one motion, the electronic stability enhancing system, and the specifications of the tow-vehicle towing the trailer assembly.

Abstract: A drive system is provided for a utility vehicle and includes an alternating-current (AC) motor for providing a drive torque. An AC motor controller receives a battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, forward/neutral/reverse (FNR) signal, and run/tow signal indicative of the utility vehicle being configured to be driven and being configured to be towed. The AC motor controller generates an AC drive signal for the AC motor, wherein the AC drive signal is based on the battery voltage signal, throttle pedal position signal, brake pedal position signal, key switch signal, FNR signal, and run/tow signal.

Abstract: A method for electric braking of a vehicle trailer and a device for vehicle trailers is provided. The vehicle trailer has a rigid hitch or drawbar arrangement (7) and is braked by the overrun forces generated as a result of braking of the tractor vehicle (2). The brake device (1) has a force measuring arrangement which can be mounted at the rigid hitch arrangement (7) and statically records the compression and tension forces acting axially on the hitch arrangement (7) using tensometer strips (24, 25) to determine the wheel brake force needed for braking via a controller that correspondingly actuates the electrical wheel brakes.

Abstract: A braking system includes a brake control system (BCS) (26) having a first output (30) and a second output (32), a first controller (34) having a brake command input (38) connected to the BCS first output (30), a direct enable input (36), an indirect enable input (44), a driver output (40) and an indirect enable output (42), a second controller (50) having a brake command input (54) connected to the BCS second output (32), a direct enable input (52), an indirect enable input (60), a driver output (56) and an indirect enable output (58).

Abstract: When an abnormality is detected in a vehicle side device such as an obstacle sensor during parking assist control, a brake control ECU ends the parking assist control and outputs a control signal to warn the driver while forcibly stopping the vehicle by outputting a first drive signal to a hydraulic brake device and generating braking force.

Abstract: An electrically controlled brake system 10 for a tractor is provided that is equipped with an anti-jackknifing brake that can be actuated by means of a manual operating element and that acts only on the brakes of a trailer coupled to the tractor. The operating element is an electrical element which generates an electrical signal to control a valve device by means of which the braking force of the anti-jackknifing brake can be increased.

Abstract: A breakaway device (10) to detect when a towed vehicle (14) separates from a towing vehicle (16) in order to engage the towed vehicle's brakes broadly comprises a sensor operable to detect when a signal from the towing vehicle (16) is lost and a shunt operable to route electrical power to the brakes. In a preferred embodiment, the sensor and the shut may be embodied in a transistor (26). In an alternative embodiment, the sensor and the shut may be embodied in an electro-mechanical switch (34). The device (10) preferably includes an override (42) and lights (44,46) to indicate the device's (10) status.

Abstract: A method for exchanging data in a vehicle train having a tractor, at least one trailer coupled to the tractor, and vehicle electronics allocated to the tractor and trailer interconnected via a PLC data bus used to provide programmed input and output functions for the vehicle electronics of the trailer. Data representing the programmed functionality is provided automatically and cyclically via the PLC data bus to the vehicle electronics. The vehicle electronics can be configured as ABS control electronics, the programmed input and output functions providing functionality beyond that of the ABS function. Control of these additional functions in the trailer vehicle electronics equipped with the specific functionality is then exercised via an input/output unit provided in the tractor and connected to the PLC data bus either directly or indirectly via the tractor ABS control electronics.

Abstract: Regenerative braking is actuated in an electrical vehicle during towing of the vehicle to recharge the battery and brake the vehicle. When a driver of a towing vehicle depresses the brakes of the vehicle (202), the electrical vehicle applies regenerative braking in proportion to a braking signal from the towing vehicle (206). Also, regenerative braking is applied to the electrical vehicle when the vehicle is inadvertently disconnected from a connector (110) that couples the electrical vehicle to the towing vehicle (208).

Abstract: A brake controller, for controlling the brakes of a towed vehicle, having a control module and a power module is provided. The control module is mounted in the cab of a vehicle used for towing, in such a manner that it can be easily seen and accessed by the driver. The control module is provided with an accelerometer, which can read acceleration forces in at least two axes, and a microprocessor which polls the accelerometer and sends braking information to the power module. The control module is also provided with a gain control, to adjust the amount of brake force information, a manual braking lever and a display panel. The power module, which may be mounted in a convenient location, preferably on the towed vehicle, receives the braking information from the control module and secures power from the towed vehicle to engage its brakes.

Abstract: A method for diagnosing a braking system using a system including a radio-based hand-held analyzer, at least one radio-based feed valve, and at least one mobile data unit. The braking system includes at least one brake pipe section, a reservoir, and at least one brake cylinder. The brake pipe section connects to the reservoir, the brake cylinder, and the radio-based feed valve. The hand-held radio-based analyzer communicates with the mobile data unit and the radio-based feed valve. The method includes retrieving brake system data and information using the hand-held analyzer, interpreting the retrieved data and information, and performing maintenance functions based on the interpretation of the data and information.

Abstract: A system (10) and method for managing an electric brake (12) in a towed vehicle (14) during a breakaway event by managing current delivery to the electric brake (12) so as to maximize both effectiveness and efficiency. A power management module (24) delivers a first level of current for a first duration in order to stop the trailer (14), and delivers a second level of current in order to hold the trailer (14) in place. When provided with feedback, the module can actively adjust the first level of current to a maximum current while avoiding locking the electric brake (12), and to adjust the second level of current to a minimum current sufficient to hold the trailer (14). Additionally, front and rear electric brakes (12A,12B) can be managed differently or independently in order to achieve the most effective and efficient result.

Abstract: A brake control system for a vehicle is comprised of a first braking device that generates a braking torque by operating a driving source of the vehicle and a second braking device that generates the braking torque by operating a hydraulic brake system of the vehicle. A controller of the brake control system is arranged to calculate a desired braking torque according to a driver's demand, to divide the desired braking torque into a low-frequency component and a high-frequency component, to command the first braking device to generate the high-frequency component, and to command at least one of the first braking device and the second braking device to generate the low-frequency component.

Abstract: A tow ball (14) is mounted to a bracket (16) by means of a spacer (20) which incorporates transducers (24) to provide signals indicating forces existing between the towing vehicle and the trailer. A control system is described which is operable to apply braking to the trailer to modify the trailer behavior independently of operation of the vehicle brakes by the operator.

Abstract: A trailer control system incorporates sensors on both the trailer and a tow vehicle towing the trailer to measure operating parameters of both the trailer and the tow vehicle or prime mover. A computer mounted in the trailer or in the tow vehicle gathers input data from the sensors, including a variety of measurements of force, displacement, and temperature for the tow vehicle, the trailer, and their components. The computer may also be used to apply braking forces to the wheels of the trailer. Using the simulator, a variety of components on the trailer may be tested, their performance measured, and a better trailer may be designed. A trailer may also incorporate such a system for better control of the trailer and the combination vehicle of which it is a part.

Abstract: An electric trailer brake controller includes a deceleration sensor for generating a brake control signal. The controller also includes a device to decrease the sensitivity of the deceleration sensor to spurious inputs. Additionally, the controller includes a brake current limiting circuit that progressively reduces the current supplied to the controlled trailer brake when the brake current exceeds a predetermined level.

Abstract: A method and system for controlling an eddy current braking system in a motor vehicle is provided. The motor vehicle includes a prime mover linked to the eddy current braking system to provide torque thereto, and the eddy current braking system has a retarder assembly including at least a rotor and a stator. The method includes the steps of detecting a feedback current from the retarder assembly, detecting a rotor speed of the rotor, providing a signal indicative of a desired retarding torque, and determining a command current for the retarder as a function of the feedback current, rotor speed and desired retarding torque using a closed-loop sliding-mode control algorithm. The command current is provided to the retarder to control application of torque to the prime mover.

Abstract: A trailer brake control system comprises a trailer. The trailer has brakes. The trailer also has a secondary electrical receiver. A towing vehicle is also provided. The vehicle has a steering wheel. The vehicle also has a secondary electrical transmitter. A steering wheel cover having a primary wireless signal transmitter is provided. The signal transmitter has a power source and a flexible torus-shaped tube. The tube has a hollow bore. Secured within the bore are a pair of wires, one flat and one toothed, offset from each other. Both wires are electronically coupled to the primary signal transmitter. A trailer brake processor is provided next. The brake processor has a trailer brake actuating switch. The actuating switch is electrically coupled with the brakes of the trailer. A primary signal receiver is coupled to the actuating switch and adapted to receive signals from the primary signal transmitter. A manual switch is also coupled to the actuating switch.

Abstract: A brake lamp illumination system for a trailer senses when the speed of the wheels decreases. If the system detects such a deceleration, the system senses whether power has been supplied to illuminate brake lamps provided on the vehicle. If no power is detected in the circuit which supplies power to the brake lamps, power is directed to the circuit to illuminate the brake lamps.

Abstract: A remote manual control is provided for an electronic wheel brake controller. The remote manual control is connected to the wheel brake controller with a cable having quick disconnect connectors at each end. Accordingly, cables having different lengths may be easily substituted for connecting the remote manual control to the wheel brake controller.

Abstract: A method and apparatus for data exchange between a towing vehicle and an attached trailer uses radio contact via transmission/receiving modules contained in the towing vehicle and in the trailer. To recognize that the towing vehicle and the trailer are connected, the transmission/receiving module of the towing vehicle transmits an identification signal, and at the same time, changes the electrical status of a connection line between the towing vehicle and the trailer. If the transmission/receiving module located in the trailer recognizes the change in the electrical status of the connection line simultaneously with receiving the transmitted identification signal, the identification signal is stored within the trailer. In subsequent communications between the towing vehicle and the trailer, the identification signal is always transmitted before the message. As such, only the attached trailer, with the appropriate stored identification signal, can communicate with its towing vehicle.

Abstract: An automated electronic brake control device comprises an upright enclosure having a separable cover, the enclosure containing an energy source, a breakaway safety switch, a controller comprising a grade and motion detection device, timer, relay and circuit breaker and means for connecting the electronic brake control device to the electrical circuity of a towing vehicle and a towed vehicle. Preferably, the brake control device is mounted upon the towed vehicle and the controller has capabilities of sensing a change of velocity in at least one direction. Electric circuitry connects the braking circuitry of the towing vehicle to the braking system of the towed vehicle such that when towing vehicle brakes are applied, the brake control device supplies power to the braking system of the towed vehicle proportional to the sensed change in velocity.

Abstract: A slave operated self-contained hydraulic brake system having an electric motor that is mounted on a gear housing. The electric motor moves a threaded rod in a lateral direction. Movement in a first direction results in contact of the rod with a master cylinder piston assembly within a master cylinder. Movement of the master cylinder piston assembly forces hydraulic fluid out of the master cylinder to actuate brakes of a towed vehicle. A pressure sensor is attached to the master cylinder and measures the hydraulic fluid pressures in master cylinder chamber. Movement of the rod in a second direction is detected by a reverse limit switch. Electrical signals are used to control the slave operated self-contained hydraulic brake system. The brake system communicates electrically with a brake control board. Sensors may be provided to provide information to a microprocessor on the control board to add control features to the brake system.

Abstract: A trailer brake control system comprises a trailer. The trailer has brakes. The trailer also has a secondary electrical receiver. A towing vehicle is also provided. The vehicle has a steering wheel. The vehicle also has a secondary electrical transmitter. A steering wheel cover having a primary wireless signal transmitter is provided. The signal transmitter has a power source and a flexible torus-shaped tube. The tube has a hollow bore. Secured within the bore are a pair of wires, one flat and one toothed, offset from each other. Both wires are electronically coupled to the primary signal transmitter. A trailer brake processor is provided next. The brake processor has a trailer brake actuating switch. The actuating switch is electrically coupled with the brakes of the trailer. A primary signal receiver is coupled to the actuating switch and adapted to receive signals from the primary signal transmitter. A manual switch is also coupled to the actuating switch.

Abstract: An automated electronic brake control device comprises an upright enclosure having a separable cover, the enclosure containing an energy source, a breakaway safety switch, a controller comprising a grade and motion detection device, timer, relay and circuit breaker and means for connecting the electronic brake control device to the electrical circuity of a towing vehicle and a towed vehicle. Preferably, the brake control device is mounted upon the towed vehicle and the controller has capabilities of sensing a change of velocity in at least one direction. Electric circuitry connects the braking circuitry of the towing vehicle to the braking system of the towed vehicle such that when towing vehicle brakes are applied, the brake control device supplies power to the braking system of the towed vehicle proportional to the sensed change in velocity.

Abstract: An electric trailer brake control device includes a delay circuit to prevent actuation of the trailer brakes when the towing vehicle hazard flasher is actuated.

Abstract: A brake control unit provides a properly oriented brake control display irrespective of whether the brake control unit is installed in a normal or inverted mode. The brake control unit determines whether a brake control signal is asserted when the brake control unit is connected to a vehicle power supply. If so, the brake control display is inverted. Alternatively, the brake control unit determines orientation by monitoring a position sensitive device. The brake control unit is also capable of determining and displaying the status of a brake load on the brake control display. In addition, the brake control unit is capable of determining and displaying an output voltage of the brake control unit on the brake control display.

Abstract: An electronic brake controller for controlling the brakes of a towed vehicle in response to commands from the towing vehicle. The controller implements a microcontroller (10) that works in conjunction with analog circuit technology.

Abstract: A system and method are provided for controlling brakes on a trailer being towed by a towing vehicle. The system includes an accelerometer for sensing inclination and a rate of deceleration of the towing vehicle and providing inclination and rate of deceleration control signals indicative thereof. A controller is provided that is responsive to the inclination and rate of deceleration control signals received from the accelerometer. The controller is operatively connected to an amplifier and these functions together to send a proportionate brake amperage output signal to control the brakes on the trailer.

Abstract: The present hostler control of a computer control train brake system combines the computer control of the train and locomotive brake system with a manual control during a hostler mode to provide soft and safe operation of the vehicle. Interlocks provide efficient and safe transferring of the controls between the computer control brake system and the manual hostler control portion. The computer control train brake system includes an electropneumatic brake controller which automatically applies the independent brake once the hostler lead mode is determined. Next, the brake controller charges the brake pipe to release the train brakes. Control of the independent brake is transferred to a pneumatic independent brake control valve of the hostler stand after the brake pipe has been charged sufficiently to fully release the train brakes. The brake pipe is charged or the train brakes are released only after the independent brake application has reached a predetermined value.

Abstract: An electrical short circuit protection device for an electric trailer brake controller includes a fuse connected between the controller and the trailer brakes and an acoustic piezoelectric transducer connected across the fuse. Upon a short circuit fault developing in the trailer brakes, the fuse opens and the transducer generates an audio warning signal.

Abstract: An operating apparatus for a parking brake is provided with a parking brake switch and an engine key switch. The parking brake switch can be operated to an ON position, an OFF position and a RESET position. When the engine key switch is OFF, the parking brake maintains an engaged state regardless of the operating position of the parking brake switch. When the engine key switch is switched from OFF to ON, the parking brake is released only when the parking brake switch is first operated to the RESET position. Then, after the parking brake switch is operated to the RESET position, the parking brake is released when the parking brake switch is operated to the OFF position, but it is engaged if the parking brake switch is operated to the ON position. With this, the parking brake is released through one and the same operating procedure, regardless of the operating position of the parking brake switch.