SYSTEMS AND METHODS FOR MONITORING AND CONTROLLING TRACTOR/TRAILER VEHICLE SYSTEMS

Abstract: A status of a subsystem positioned on a trailer is communicated to a tractor electrically and mechanically connected to the trailer. A spread spectrum data communications signal representing a status of the subsystem is produced on the power bus. A status of the subsystem is determined from the spread spectrum data communications signal. Preferably, the status of the subsystem is indicated to an operator positioned on the tractor. A command for controlling a subsystem on a trailer is communicated from a tractor to the trailer over a power bus. A spread spectrum data communications signal representing the command is produced on the power bus, and the subsystem is controlled based on the spread spectrum data communications signal. Preferably, the command is received from an operator positioned on the tractor.

Description: SYSTEMS AND METHODS FOR MONITORING AND CONTROLLING TRACTOR/TRAILER VEHICLE SYSTEMS Field of the Invention This invention relates generally to data communications in a combination of a tractor and a trailer, more specifically, to data communications systems and methods for monitoring and controlling systems of a tractor/trailer. Background of the Invention The trucking industry has for many years used tractor/trailer combinations to transport cargo over the roadways to intended destinations. As shown in Fig. 1, tractor 10 and trailer 20 are mechanically coupled together so that the tractor can pull the trailer with its cargo in an efficient and cost effective manner. Various links between the tractor and the trailer provide vehicle subsystems with power and/or control signals to operate. Hydraulic, pneumatic, electrical and other subsystems on the tractor/trailer combination have associated electrical conductors and pneumatic lines running therebetween so these subsystems can operate. With respect to electrical subsystems, a tractor/trailer combination typically includes a tractor 10 and trailer 20 and a power bus 30 electrically connected to one or more batteries 32, which are typically charged by an alternator 34 mechanically driven by a tractor engine 15. Thus, electrical power is distributed from tractor 10 to subsystems in trailer 20. The trucking industry has historically lagged behind other industries with respect to technological innovation, but recently has been incorporating more and more sophisticated electronic subsystems in both tractors and trailers. For example, regulatory changes arising from safety concerns have led to the incorporation of trailer antilock braking systems (ABS) , frequently microprocessor-controlled, in trailers in order to minimize the risk of trailer skids and jackknifing. New trailers are being constructed with ABS, while older trailers are being retrofitted to incorporate ABS. These systems may include, for example, actuators and transducers operatively connected to the trailer wheels and braking hardware, controlled by electronic circuits located elsewhere on the trailer and tractor. As shown in Fig. 1, an antilock braking system 100, as well as other subsystems, conventionally receives electrical power from power bus 30. Antilock braking systems may produce data signals which indicate various conditions of the ABS. These data signals may include, for example, a failure warning signal which is asserted if an ABS microprocessor detects a failure within itself or other components of the ABS. In some applications, a data signal may drive a light-emitting diode (LED) or other indicator. Conventionally, the tractor/trailer operator has no external indication of the state of the ABS. Even those systems having an external indicator may not allow a tractor/trailer operator to inspect the state of the ABS while positioned in the tractor cab with the tractor/trailer combination in operation. The operator typically may have to park the vehicle, exit the cab, and inspect an ABS indicator on the trailer, if present, in order to monitor the state of- the ABS. Thus, it may be difficult for the operator to monitor the state of the ABS system while the vehicle is moving. It may be possible to wire data signals from an ABS to a tractor using a dedicated signal path such as a twisted wire pair passed from the trailer to the tractor. A seven-pin connector has been widely used by the trucking industry to convey electrical power for lighting and equipment operation between a tractor and a trailer. As shown in Fig. 2, the connector 40 includes two disengageable connector portions 50 and 60 to permit the tractor and trailer combination to be disconnected. An example of such a seven-pin connector is illustrated in U.S. Patent No. 4,969,839 to Nilsson, the entire disclosure of which is specifically incorporated herein by reference. These seven-pin connectors are well known and have been specified by the Society of Automotive Engineering (SAE) according to the standard number "SAE J560" the teachings of which are also incorporated herein by reference. Each of the sockets 54 in the standard seven-pin connector (SAE J560) is an electrical conductor carried by the plug portion 50 of the connector and which is adapted to mate with a corresponding electrical pin 63, also an electrical conductor, in the receptacle portion 60 of the connector to thereby provide an electrical signal between the tractor and the trailer. The pins and corresponding sockets generally are assigned to specific electrical subsystems, for example, power, ground, turn signals, brake lights, clearance lamps, emergency flashers, and other devices requiring electrical signals. The seventh pin on the connector is usually an "auxiliary" pin which can be used for specific electrical purposes or applications on individual tractor/trailer combinations. Although pins and sockets of the seven-pin connector may be used to convey an ABS status signal to a tractor, the generally limited circuit capacity afforded by the standardized connector would be reduced even further. The standard seven-pin connector simply may not provide the circuit capacity needed to convey to a tractor an increased number of data signals from various systems located on trailers, including additional ABS systems which may be present when a tractor is connected to multiple trailers. Connectors with greater capacity could be employed, but the seven-pin connector (SAE J560) is an industry standard for tractor/trailers. Alternative communications techniques such as fiber optic links or radio communication through free space may bypass the bottleneck of limited channel capacity in the standard connectors used to connect tractors and trailers, but may require the installation of complex and expensive electronic components. These components, often referred to as "black boxes," may be vulnerable to theft and vandalism when placed on trailers which often are under the control of multiple operators and left in unsecured areas. Summary of the Invention In view of the foregoing, it is therefore an object of the present invention to provide systems and methods for data communication in a tractor and/or a trailer. It is another object of the present invention to provides data communications systems and methods which utilized existing wiring on tractors and trailers. It is another object of the present invention to provide data communications systems and methods that are also compatible with standardized connectors widely used in the trucking industry. It is another object of the present invention to provide data communications systems which are less sensitive to the interference and noise frequently present in tractor and trailer electrical systems. It is another object of the present invention to provide systems and methods for monitoring a warning system of a tractor/trailer combination. It is another object of the present invention to provide systems and methods for monitoring an antilock braking system of a tractor/trailer combination by a tractor/trailer operator positioned in a cab of a tractor. It is another object of the present invention to provide systems and methods for monitoring an antilock braking system which allow a trailer equipped with elements of an antilock braking system monitoring system to be used with a tractor which is not equipped with complementary elements while still providing an indication of a status of the antilock braking system to a tractor/trailer operator positioned within the tractor cab. It is another object of the present invention to provide systems for monitoring an antilock braking system in a tractor/trailer combination using components packaged to be inconspicuous and less vulnerable to theft and vandalism. These and other objects, features and advantages of the present invention are provided by systems and methods for communicating antilock braking signals to a status indicator via the power bus which distributes power to the antilock braking system. Thus, a tractor connected to a trailer having an antilock braking system and an antilock braking system interface which produces a data signal which is input into an ABS reporting system that includes power line carrier communicating means for communicating a data communications signal representing a status of the antilock braking system over a power bus thai distributes power to the antilock braking system, and status determining means for determining a status of the antilock braking system from the data communications signal. The status determining means preferably includes an indicator which indicates the determined status to a tractor/trailer operator positioned within the cab of the tractor. The present invention provides for remote monitoring an antilock braking system by a tractor/trailer operator. Thus, the present invention allows a tractor/trailer operator to monitor an antilock braking system while the operator is positioned in the tractor cab and the tractor/trailer combination is in motion. The present invention also provides for monitoring of the status of an antilock braking system without requiring extensive rewiring of the tractor or the trailer. Furthermore, the present invention provides for monitoring of an antilock braking system using existing power wiring and connectors. In particular, an antilock braking system monitoring system according to the present invention includes a tractor and a trailer connected thereto. The trailer includes an antilock braking system and an antilock braking system interface which produces a data signal representing a status of the antilock braking system. A power bus distributes electrical power to the antilock braking system. Power line carrier communicating means are responsive to the antilock braking system and produce a data communications signal on the power bus from the data signal . The status determining means is responsive to the antilock braking system and determines a status of the antilock braking system from the data communications signal. The power line carrier communicating means may include a waveform generator, preferably an oscillator, which produces a power line carrier signal having a predetermined carrier frequency. A modulator is responsive to the waveform generator and the antilock braking system and produces the data communications signal from the power line carrier signal and the data signal. Coupling means couples the modulator to the power bus and superposes the data communications signal on the power bus. The status determining means may include power line carrier receiving means that is responsive to the power bus and receives the data communications signal. Processing means is responsive to the power line carrier receiving means and produces a data- modulated digital carrier signal from the received data communications signal. Detecting means detects a status of the antilock braking system from a count of the transitions of the data-modulated digital carrier signal occurring during a predetermined time interval. The status determining means may also include an indicator for indicating the determined status to a tractor/trailer operator positioned within a cab of the tractor, thus informing the operator of the condition of the antilock braking system while the tractor/trailer combination is in operation. The indicator may be in the form of lights, gauges, images on a CRT screen, audible annunciators and the like, as would be readily understood by those skilled in the art. The power bus may include a plurality of tractor power lines and trailer power lines electrically connected by a connector. The connector may include an industry-standard SAE J560 connector. Thus the present invention provides for monitoring of an antilock braking system using existing wiring and connectors. In another aspect of the present invention, power line communicating means may be integrated with a warning indicator in a trailer warning indicator package. The warning indicator is responsive to the antilock braking system interface and indicates a status of the antilock braking system from the data signal . The trailer warning indicator package includes means for mounting the trailer warning indicator package so that it is positioned on the trailer and viewable by a tractor/trailer operator positioned within the tractor cab. Thus, a trailer which incorporates the power line carrier communicating means of an antilock braking system according to the present invention may be used with a tractor which is not equipped with the complementary status determining means, while still providing a way to indicate a status of the trailer antilock braking system to a tractor/trailer operator positioned within the tractor cab. The trailer warning indicator package preferably has a standard form factor, such as that of the standard running lights commonly used on trailers, thereby providing components of an antilock braking system monitoring system which are inconspicuous and less susceptible to vandalism and theft. According to another aspect of the present invention, a communications system for communicating a status of a subsystem positioned on a trailer to a tractor includes a power bus which supplies electrical power to the combination of the tractor and the trailer, and spread spectrum signal producing means, responsive to the subsystem and positioned on the trailer, for producing a spread spectrum data communications signal representing a status of the subsystem on the power bus. Status determining means, positioned on the tractor, is responsive to the power bus, for determining a status of the subsystem from the spread spectrum data communications signal. The subsystem may produce a status signal representing a status of the subsystem, and the spread spectrum signal producing means may include means for producing the spread spectrum data communications signal from the status signal. The status determining means may include spread spectrum signal receiving means, positioned on the tractor responsive to the power bus, for receiving the spread spectrum data communications signal, and means, positioned on the tractor and responsive to the spread spectrum signal receiving means, for determining a status of the subsystem from the received spread spectrum data communications signal. The status determining means also preferably includes an indicator, such as an alphanumeric display, an a LED display, or an audio annunciator, which indicates a status of the subsystem to an operator positioned in the tractor. According to another aspect, a communications system for connecting to a combination of a tractor and a trailer mechanically and electrically connected to the tractor to communicate a command from the tractor to a subsystem positioned on the trailer includes a power bus which supplies electrical power to the combination of the tractor and the trailer, spread spectrum signal producing means, positioned on the tractor and responsive to the subsystem, for producing a spread spectrum data communications signal representing the command on the power bus, and controlling means, positioned on the trailer, for controlling the subsystem based on the spread spectrum data communications signal . The controlling means preferably includes spread spectrum signal receiving means, positioned on the trailer and responsive to the power bus, for receiving the spread spectrum data communications signal, and means for controlling the subsystem from the received spread spectrum data communications signal. The system also preferably includes operator input means for receiving a command from an operator positioned on the tractor, .such as a switch mounted on an instrument cluster in the tractor. According to the present invention, a communications module for connecting to a trailer having a power bus for receiving power from a tractor mechanically and electrically connected to the trailer includes a status signal input and a command signal output. Spread spectrum signal producing means, responsive to the status signal input, produce a spread spectrum data communications signal from a status signal provided at the status signal input. The spread spectrum signal producing means is coupled to the power bus such that a spread spectrum data communications signal produced by the spread spectrum signal producing means is superposed on the power bus . The module also includes spread spectrum signal receiving means for receiving a spread spectrum communications signal and produces a command signal at the command signal output from the received spread spectrum communications signal, coupled to the power bus such that a spread spectrum data communications signal superposed on the power bus is received by the spread spectrum signal receiver. The module also preferably includes a communications module housing which houses the spread spectrum signal receiving means and the spread spectrum signal producing means, and for mounting the communications module housing to a trailer. A communications module for connecting to a tractor having a power bus which supplies electrical power to the tractor includes a command input and spread spectrum signal producing means, responsive to the command input, for producing a spread spectrum data communications signal from a command provided at the command input, coupled to the power bus such that a spread spectrum data communications signal produced by the spread spectrum signal producing means is superposed on the power bus. Spread spectrum receiving means for receiving a spread spectrum communications signal is coupled to the power bus such that a spread spectrum data communications signal superposed on the power bus is received by the spread spectrum signal receiver. The module preferably includes status determining means, responsive to the spread spectrum receiving means, for determining a status of the subsystem from the received spread spectrum data communications signal, preferably an indicator which indicates a status of the subsystem. The module also preferably includes operator input means for receiving a command from an operator, such as a switch. The module also preferably includes a communications module housing which houses the spread spectrum signal producing means, the spread spectrum signal receiving means, the indicator and the operator input means, and means for mounting the communications module on the tractor such that the indictor is viewable by an operator positioned on the tractor and the operator input means is accessible to an operator positioned on the tractor. Monitoring methods according to the present invention are used for monitoring an antilock braking system of a combination of a tractor mechanically and electrically connected to a trailer having an antilock braking system and an antilock braking system interface which produces a data signal representing a status of the antilock braking system. These methods include the following steps: a data communications signal is produced from the data signal; the data communications signal is communicated over a power bus; and a status of the antilock braking system is determined from the data communications signal. The step of communicating may include steps of modulating the data signal with a signal having either a predetermined carrier frequency or a predetermined spectrum of carrier frequencies to produce the data communications signal and superposing the data communications signal on the power bus. The step ' of determining may include the step of indicating the determined status of the antilock braking system to a tractor/trailer operator positioned within a cab of the tractor. A method for determining a status of an antilock braking system from a data communications signal representing a status of the antilock braking system is also provided by the present invention. The method includes the steps of: receiving a data communications signal representing a status of an antilock braking system; producing a data-modulated digital carrier signal from the received data communications signal; and detecting a status of an antilock braking system from a count of transitions of the data-modulated digital carrier signal occurring during a predetermined time interval . Brief Description of the Drawings Some of the objects and advantages of the present invention having been stated, others will be more fully understood from the detailed description that follows and by reference to the accompanying drawings in which: Fig. 1 is a schematic diagram illustrating a combination tractor/trailer as in the prior art; Fig. 2 is an isometric exploded view illustrating a prior art SAE J560 connector; Fig. 3 is a schematic diagram illustrating an antilock braking system monitoring system according to an embodiment of the warning system of the present invention; Fig. 4 is a block diagram illustrating power line carrier communicating means according to the present invention; Fig. 5 is a block diagram illustrating status determining means according to the present invention; Fig. 6 is an electrical schematic -diagram illustrating an electrical circuit for communicating a data ' communications signal over a power bus according to the present invention; Fig. 7 is an electrical schematic diagram illustrating an electrical circuit for determining a status of an antilock braking signal from a data communications signal received from a power bus according to an embodiment of a warning system of the present invention; Figs . 8A-B are software block diagrams illustrating operations used in determining a status of an antilock braking system from transitions of a data communications signal according to the present invention; Fig. 9A is a schematic diagram illustrating a tractor/trailer combination with an antilock braking system monitoring system according to an embodiment of a warning system of the present invention; Fig. 9B is a perspective drawing illustrating an instrument cluster of a tractor including an indicator according to the present invention; Fig. 10 is a schematic diagram illustrating a tractor/trailer combination with a warning indicator according to the present invention; Fig. 11 is a schematic diagram illustrating an intelligent warning indicator according to the present invention; Fig. 12 is a schematic diagram illustrating a tractor connected to multiple trailers including an antilock braking system monitoring system according to an embodiment of a warning system of the present invention; Fig. 13 is a block diagram illustrating an embodiment of a communications system according to the present invention; Fig. 14 is a block diagram illustrating an embodiment of a communication system according to the present invention; Fig. 15 is a block diagram illustrating an embodiment of a communications system according to the present invention; Fig. 16 illustrates embodiments of communications modules according to the present invention; Fig. 17 is a block diagram illustrating an embodiment of a trailer communications module according to the present invention; Fig. 18 is a block diagram illustrating an embodiment of a tractor communications module according to the present invention; and Fig. 19 illustrates an embodiment of a tractor communications module according to the present invention. Detailed Description of Preferred Embodiments The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art . Like numbers refer to like elements throughout. Fig. 3 illustrates an antilock braking system monitoring system according to the present invention. The antilock braking system 100 receives electrical power 35 from the power bus 30. An antilock braking system interface 110, responsive to the antilock braking system 100, produces a data signal 105 representing a status of antilock braking sy_stem 100. Data signal 105 may be a binary signal representing an either/or condition of the antilock braking system 100 such as failed/operational, active/standby, and the like. As many antilock braking systems employ microprocessor-based controllers, the antilock braking system interface may be located within the antilock braking system 100 and the data signal 105 may be a digital signal produced by the antilock braking system controller. It will be understood by those skilled in the art that various forms of antilock braking system interface 110 may be used with the present invention, such as relays or switches electrically connected to control signals of antilock braking system 100, transducers mechanically or electrically connected to components of antilock braking system 100, and the like. The data signal 105 may be digital as described above, or may be an AC or DC analog signal, the amplitude, frequency and other parameters of which may provide information. The power line carrier communicating means 320 is responsive to antilock braking system interface 110 and produces the data communications signal 325 superposed on power bus 30. As illustrated in Fig. 4, the power line carrier communicating means 320 preferably includes a modulator 410 which modulates a carrier signal 425, produced by a waveform generator 420 which may be an oscillator, with data signal 105. Electrical coupling means 430 couples the modulator 410 to the power bus 30, superposing the data communications signal 325, in the form of a data- modulated carrier signal, on the power bus 30. Power line carrier techniques for superposing a modulated carrier signal on a power bus and receiving the superposed signal from the power bus are known for other applications. It will be understood by those skilled in the art that the modulator 410 may perform amplitude modulation, frequency modulation, .phase modulation and other modulation functions. It will also ' be understood that the electrical coupling means 430 may utilize inductive coupling, capacitive coupling, a combination of inductive and capacitive coupling, and other methods to superpose the data communications signal 325 on the power bus 30. It will be understood by those skilled in the art that superposing refers to any linear or nonlinear combination of signals in transmission media such as wires, busbars, and the like. Fig. 6 is an electrical schematic diagram of an exemplary embodiment according to the present invention, illustrating an electrical circuit which performs functions of the power line carrier communicating means 320. For example, an LM555 timer IC Ul preferably produces a carrier signal having a predetermined frequency such as approximately 125 kHz at a carrier signal output node CARRIER when the voltage at an input node ABS, where the data signal 105 is input, is above a predetermined level, preferably approximately 12 volts. The signal at the carrier signal output node CARRIER drives the base of transistor Ql. This induces a sinusoidal current between terminals 5,6 of a transformer Tl which is capacitively coupled through a capacitor C7 to a power bus 30 present at a power bus output node BAT. Thus, modulation of the carrier signal at the carrier signal output node CARRIER by the data signal 105 at the input node ABS is effected, producing the data communications signal 325 superposed on the power bus 30. It will be understood by those skilled in the art that the power line carrier communicating means 320 may be implemented using various circuits and techniques. For example, the power line carrier communicating means 320 may perform signal processing on the data signal 105 or combine the data signal 105 with other signals in an encoded data stream, which is used to modulate a carrier signal and superposed on the power bus 30. The waveform generator 420 may be integrated into the antilock braking system 100 or another electronic system present on the tractor or trailer. The ABS system 100 may also be a pressure monitoring system, a temperature monitoring system, or other subsystem so that the status of the system is indicated or warned to others such as an operator positioned in the cab of a tractor. In the embodiment illustrated in Fig. 6 the data signal 105 present at the input node ABS corresponds to a voltage supplied by the antilock braking system interface 110, but it will be understood that the data signal 105 may be coupled into modulator 420 in various other ways, such as optical and magnetic coupling. It will be understood by those skilled in the art that power line carrier communicating means 320 may be centralized or distributed. It will also be understood that power line carrier communicating means 320 may include other means for processing data signal 105, such as signal processing or coding functions implemented using special purpose hardware or a combination of special purpose hardware and general purpose hardware running software. Preferably, the power line carrier communicating means 320, however, includes means for communicating data, which may include a modulator, over a predetermined spectrum of frequencies such as illustrated by the spread spectrum technology embodied in the integrated circuits and components (i.e., Intellon SSC PLCEFN, XCR38149PR02, QHCK-9409 integrated circuit or CEBus-compliant communications modules according to EIA RS-232 and ISA bus module standards) of the Intellon Spread Spectrum Carrier of the Intellon Corporation of Ocala, Florida which are hereby incorporated herein in its entirety by reference. As understood by those skilled in the art, a spectrum (e.g., 100-400 KHz) of frequencies for data communications allows the signal to be communicated in a manner over the power line which significantly reduces the interference or suppression of the received signal by other electromechanical systems in the tractor such as the alternator. An antilock braking system monitoring system according to the present invention may also include a warning indicator 1000 as shown in Figs. 10 and 11. The warning indicator 1000 preferably is packaged with power line carrier transmitter means 320 in a trailer warning indicator package 1100, producing an "intelligent warning indicator" as illustrated in Fig. 11. The trailer warning indicator package 1100 is positioned on trailer 20 so that the warning indicator 1000 is visible to a tractor/trailer operator 1020 positioned within a tractor cab 1010, as shown in Fig. 10, thus providing a way to indicate a status of the antilock braking system 100 to a tractor/trailer operator even if the tractor 10 is not equipped with status determining means 330. Preferably, the warning indicator 1000 is powered by the data signal 105, but it will be understood by those skilled in the art that the warning indicator 1000 may be directly actuated by the data signal 105 or indirectly actuated by such devices as relays, lamp drivers and the like. The trailer warning indicator package 1100 also preferably has an inconspicuous standard form factor, such as that used for the running lights commonly used on trailers, to thereby reduce the risk of vandalism or theft. Referring again to Fig. 3, status determining means 330 determines a status 335 of antilock braking system 100 from the data communications signal 325 superposed on the power bus 30 by the power line carrier communicating means 320. As shown in Fig. 5, the status determining means 330 preferably includes power line carrier receiving means 510 for receiving the data communications signal 325 from the .power bus 30, processing means 520 for producing a data-modulated digital carrier signal 525 from the received data communications signal 325, and detecting means 530 for detecting a status 535 of the antilock braking system 100 from transitions of data-modulated digital carrier signal 525. It will be understood by those skilled in the art that the status determining means 330, processing means 520 and detecting means 530 may be centralized or distributed. The status determining means 330, processing means 520 and detecting means 530 may also be implemented using special purpose hardware or a combination of special purpose hardware and general purpose hardware running software. Fig. 7 is an electrical schematic diagram of an exemplary embodiment according to the present invention, illustrating an electrical circuit which performs functions of status determining means 330. Data communications signal 325, here an amplitude- modulated signal produced by a power line carrier communicating circuit of the type shown in Fig. 5, is received by a resonant tank circuit including capacitors C5 and C6 and inductor Ll from power bus 30 present at a power bus input node VPWRIN. The received signal is capacitively coupled through capacitor C7 into multistage level-changing and shaping circuits including transistors Q5-Q8. As will be understood by those skilled in the art, these circuits produce a first data-modulated digital carrier signal at a first digital carrier signal output node LOGIC with the same carrier frequency as the received data communications signal 325. In the illustrated embodiment, the first data-modulated digital carrier signal at the first digital carrier signal output node LOGIC is then divided in counter IC U2 to produce a second data- modulated digital carrier signal at a second digital carrier signal output node PIN which has a carrier frequency l/128th of the first data-modulated digital carrier signal at the second node LOGIC. The second data-modulated digital carrier signal is then input into a programmable controller IC U3 having operating software which counts transitions of the second data- modulated digital carrier signal, illuminating an external light-emitting diode (LED) LED if the number of transitions occurring in the second data-modulated digital carrier signal occurring during a predetermined time interval is above a predetermined threshold, indicating a state of data signal 325. Figures 8A-B illustrate exemplary operations for the programmable controller chip TJ3 of Fig. 7. A pair of software counters control a main routine 800 and a sampling routine 850. One of the software counters is a first software hit count which counts the number of times a transition is detected in the second data-modulated signal at the second digital carrier signal output node PIN, while the other software counter is a loop count which keeps track of the number of times the second data-modulated signal is sampled during the sampling routine 850. The main routine 800 determines if the external light-emitting diode LED is already in an "on" state 801. If it is, the sampling routine 850 is called, shown in Fig. 8B. The two software counts are initialized 851 and the external counter IC U2 is cleared 852. The sampling routine waits to see if a transition occurs in the second data-modulated digital carrier signal at the second digital carrier signal output node PIN during a predetermined time interval, preferably within 823 to 1280 milliseconds from the time the external counter IC TJ2 is cleared. If a transition occurs during the predetermined time interval, a software hit count is incremented 854. If not, the software loop count is incremented 855. If the loop count is less than a predetermined number 856, preferably 500, the routine returns to clear the external counter IC 852. If not, the sampling routine is exited 857. Returning to Fig. 8A, if the program returns to the main routine 800 from the sampling routine 850 and the software hit count is less than a predetermined number, preferably 50, the main program recalls the sampling program 804. The sampling routine is called three times. After the final iteration 807, if the returned software hit count is less than a predetermined number, preferably 50, the diode LED is turned off before returning to the main program 800. If the diode LED is off entering the main 800, the main routine calls the sampling program once 809. If the returned software hit count is greater than a predetermined number, preferably 400, then the diode LED is turned off . Techniques for demodulating a modulated carrier signal are known in other applications. It will be understood by those skilled in the art that the exemplary operations of Figs. 8A and 8B provide sufficient hysteresis in the detection of the transitions of a modulated digital carrier signal to provide noise-resistant demodulation of the data- modulated signal 325. It will also be understood that other means of demodulating data-modulated digital carrier signal 325 may be used with the present invention. Fig. 9A illustrates an aspect of the present invention, showing status determining means 330 located in tractor 10. Power bus 30 is shown including a plurality of trailer power lines 910 connected to a plurality of tractor power lines 915 by a connector 920. Connector 920 preferably is an industry standard seven-pin SAE J560 as illustrated in Fig. 2. As shown in Fig. 9B, status determining means may include an indicator 950, here shown as a visual indicator 960 mounted on a tractor instrument cluster 970. It will be understood by those skilled in the art that indicator 950 may include other devices to indicate status of an antilock braking system to an operator of a tractor/trailer combination, including visual displays such as CRT's and lights, and audible annunciators. It will be also understood by those skilled in the art, status determining means 330 may be positioned elsewhere, including on the trailer. Fig. 12 illustrates another aspect of the present invention, showing a tractor 10 connected to multiple trailers 20. Trailers 20 may each include an antilock braking system 100 and an antilock braking system interface 110 producing a data signal 105. Each data signal 105 may be used to produce a data communications signal 325 which is superposed on the power bus 30. Status determining means 330 determines statuses of antilock braking systems 100 from the data communications signals 325. It will be understood by those skilled in the art that although data communications signals 325 may each have a unique predetermined carrier frequency allowing them to be separately received, power line carrier communicating means 320 and status determining means 330 may utilize, for example, time-multiplexing, code-multiplexing or other signal processing techniques to allow data communications signals 325 to have the same carrier frequency. Figs. 3-5 illustrate operations for monitoring an antilock braking system of a tractor/trailer operation according to the present invention. A data communications signal 325 is produced in power line carrier communicating means 320 from a data signal 105 representing a status of an antilock braking system 100 produced by an antilock braking system interface 110. The data communications signal 325 is superposed on a power bus 30 by power line carrier communicating means 320. A status 335 of the antilock braking system 100 is determined from the data communications signal 325. The data communications signal 325 may be produced by modulating a carrier signal 425 having a predetermined carrier frequency by the data signal 105. The data communications signal may be superposed on power bus 30 by electrical coupling means 430, as illustrated by Fig. 4. The data communications signal 325 may be received by power line carrier receiving means 510, as shown in Fig. 5. The received data modulated carrier signal may be processed by processing means 520 to produce a data-modulated digital carrier signal 525. A status 535 of the antilock braking system 100 is detected from a count of transitions of the data-modulated digital signal 525 occurring during a predetermined time interval. It has been found, according to the present invention, that spread spectrum technology, not generally used in tractor/trailer power line communications, is particularly suitable for the electrical environment of tractor/trailer systems. The energy of a spread spectrum data communications signal is spread across a broad range of frequencies such that even if one component is subject to coherent interference, the signal can still be reliably recovered. As the signal energy is widely distributed across a relatively wide spectrum, spread spectrum data communications systems tend to interfere less with coherent receivers such as radios. In contrast, the conventional modulation techniques utilized in some power line carrier systems is generally susceptible to interference from coherent electrical signals, such as those generated on the power bus of the tractor/trailer by switching transients from an alternator. In addition, because of the coherent nature of conventionally modulated signals, conventionally modulated signals may interfere with systems such as citizens' band (CB) radios, stereo systems, and navigation systems. As illustrated in Fig. 13, a preferred embodiment of communications system 1300 for a tractor/trailer combination according to the present invention includes bidirectional communicating means 1305 for communicating a first spread spectrum data communications signal 1341 representing status of a first subsystem from a trailer 20 to a tractor 10 and for communicating a second spread spectrum data communications signal 1311 representing a command to a second subsystem from the tractor 10 to the trailer 20, the spread spectrum data communications signals 1311, 1341 being superposed on a power bus 30. First spread spectrum signal producing means 1340, positioned on a trailer 20 and responsive to the first subsystem, produces the first spread spectrum data communications signal 1341 on the power bus 30. First spread spectrum signal receiving means 1320, positioned on the tractor 10 and responsive receive the first spread spectrum data communications signal 1341. Second spread spectrum signal producing means 1310, positioned on the tractor 10 and electrically coupled to the power bus 30, produces the second spread spectrum data communications signal 1311. Second spread spectrum signal receiving means 1320, positioned on the trailer 20 and responsive to the power bus 30, receives the second spread spectrum data communications signal 1311. Fig. 14 illustrates a preferred embodiment of a communications system 1400 for communicating a status of a subsystem 100, e.g., an antilock braking system, a trailer refrigeration system, a door sensor and the like. Spread spectrum signal producing means 1430, positioned on a trailer 20, produces a spread spectrum data communications signal 1431 on a power bus 30, the spread spectrum data communications signal 1.431 representing a status of the subsystem 100. Preferably, the spread spectrum data communications signal 1431 is produced from a status signal 101 produced by the subsystem 100. Status determining means 1410, positioned on a tractor 10, determines a status 1411 from the spread spectrum communications signal 1431. Preferably, status determining means 1410 includes spread spectrum signal receiving means 1420 for receiving the spread spectrum data communications signal 1431. Fig. 15 illustrates a preferred embodiment of a communications system 1500 for communicating a command to a subsystem 100, e.g., an antilock braking system, a trailer lighting system, and the like, from a tractor 10 to a trailer 20. Spread spectrum signal producing means 1510 produces a spread spectrum data communications signal 1511 representing the command, on a power bus 30. Controlling means 1520 controls the subsystem 100 based on the spread spectrum data communications signal 1511. Preferably, the controlling means 1520 includes spread spectrum signal receiving means 1522 for receiving the spread spectrum data communications signal 1511. As illustrated in Fig. 16, the means of Figs. 14 and 15 may be included in a tractor communications module 1610 and a trailer communications module 1630 for connecting to a power bus 30. The trailer communications module includes a communications module housing 1635, which houses the module components, and means 1632 for mounting the housing 1435 to a trailer, such as a mounting flange with holes drilled therein. The trailer communications module 1630 preferably includes means 1640 for electrically connecting the module to the power bus 30, a status signal input 1651, and a command signal output 1652, here illustrated as pigtail connections, although those skilled in the art will understand that other devices may be employed for the connecting means 1640, the input 1651 and the output 1652, such as connectors. The tractor communications module 1610 preferably includes a communications module housing 1615 which houses the module components, and means 1518 for mounting the module 1610 to a tractor, such as a mounting flange with mounting holes drilled therethrough. The tractor communications module 1610 preferably includes an indicator such as an alphanumeric display 1612 and LED displays 1616, which indicates a status to an operator, as well as operator input means such as a membrane switch 1614 positioned on the module 1610, for receiving a command from an operator, as well as means 1620 for electrically connecting the module 1610 to the power bus 1620. A preferred embodiment of a trailer communications module 1630 includes the spread spectrum signal producing means 1430 of Fig. 14, and the controlling means 1520 of Fig. 15, implemented as shown in FIG. 17 using a microcontroller 1720 connected to input and output buffer circuits 1730, 1740 and a spread spectrum transceiver 1710, preferably a CEBus compliant transceiver such as the above-mentioned CEBus-compliant devices produced by the Intellon Corporation. In particular, these devices employ spread spectrum techniques and contention- resolving/collision detecting data transfer protocols to improve data communications, as described in U.S. Patent 5,090,024 to Vander Mey et al . These devices are designed to interface with a microcontroller or similar data processor via a parallel or serial data interface, producing spread spectrum data packets from data received from the processor over the interface and converting spread spectrum data packets into conventional digital signals which are conveyed to the data processor over the data interface. In a preferred embodiment of a tractor communications module 1630, the status determining means 1420 of Fig. 14 and the spread spectrum signal producing means 1510 of Fig. 15 are similarly implemented using a microcontroller 1720 and a spread spectrum transceiver 1710, as illustrated in Fig. 18. In the tractor communications module 1630, however, the microcontroller 1720 interfaces with operator input means 1614 and an indicator 1612, to receive commands from an operator and to indicate status to the operator. The use of microcontrollers to control displays and receive inputs from input devices is well- known to those skilled in the art, and need not be discussed in detail herein. As illustrated in Fig. 19, the tractor communications module 1610 may be mounted on the instrument cluster 970 of a tractor, such that the indicators 1612,1614 are viewable by an operator positioned in the tractor, and the operator input means 1514 is accessible to the operator. In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims: THAT WHICH IS CLAIMED: 1. An antilock braking system monitoring system for connecting to a trailer having an antilock braking system which produces a data signal representing a status of the antilock braking system and a power bus which distributes electrical power to the antilock braking system, the monitoring system comprising: power line carrier communicating means responsive to the antilock braking system for producing a data communications signal on said power bus from said data signal; and status determining means responsive to said power bus for determining a status of the antilock braking system from said data communications signal. 2. An antilock braking system monitoring system according to Claim 1 : wherein said power line carrier communicating means comprises spread spectrum signal producing means, responsive to the antilock braking system, for producing a spread spectrum data communications signal on said power bus from said data signal; and wherein said status determining means comprises means for determining a status of the antilock braking system from said spread spectrum data communications signal. 3. An antilock braking system monitoring system according to Claim 1 wherein said status determining means comprises an indicator which indicates a status of the antilock braking system to a tractor/trailer operator positioned within a tractor cab of a tractor connected to the trailer. 4. An antilock braking system monitoring system according to Claim 2 wherein said status determining means comprises an indicator which indicates a status of the antilock braking system to a tractor/trailer operator positioned within a tractor cab of a tractor connected to the trailer. 5. A antilock braking system monitoring system according to Claim 1 further comprising: a warning indicator which indicates a status of said antilock braking system, said warning indicator being responsive to said antilock braking system; and a trailer warning indicator package, said power line communicating means and said warning indicator being integrated in said trailer warning indicator package, said trailer warning indicator package further including means for mounting said trailer warning indicator package on the trailer so that said warning indicator is viewable by a tractor/trailer operator positioned within a tractor cab of a tractor connected to the trailer. 6. A antilock braking system monitoring system according to Claim 2 further comprising: a warning indicator which indicates a status of said antilock braking system, said warning indicator being responsive to said antilock braking system; and a trailer warning indicator package, said power line communicating means and said warning indicator being integrated in said trailer warning indicator package, said trailer warning indicator package further including means for mounting said trailer warning indicator package on the trailer so that said warning indicator is viewable by a tractor/trailer operator positioned within a tractor cab of a tractor connected to the trailer. 7. A antilock braking system monitoring system according to Claim 4 further comprising: a warning indicator which indicates a status of said antilock braking system, said warning indicator being responsive to said antilock braking system; and a trailer warning indicator package, said power line communicating means and said warning indicator being integrated in said trailer warning indicator package, said trailer warning indicator package further including means for mounting said trailer warning indicator package on the trailer so that said warning indicator is viewable by a tractor/trailer operator positioned within a tractor cab of a tractor connected to the trailer. 8. A communications system for a combination of a tractor and a trailer mechanically and electrically connected to the tractor, for communicating a status of a subsystem positioned on the trailer to the tractor, the system comprising: a power bus which supplies electrical power to the combination of the tractor and the trailer; spread spectrum signal producing means, responsive to the subsystem and positioned on the trailer, for producing a spread spectrum data communications signal representing a status of the subsystem on the power bus; and status determining means, positioned on the tractor and responsive to the power bus, for determining a status of the subsystem from the spread spectrum data communications signal. 9. A system according to Claim 8, wherein the subsystem produces a status signal representing a status of the subsystem, and: wherein said spread spectrum signal producing means comprises means for producing said spread spectrum data communications signal from the status signal; and wherein said status determining means comprises : spread spectrum signal receiving means, positioned on the tractor responsive to the power bus, for receiving said spread spectrum data communications signal; and means, positioned on the tractor and responsive to said spread spectrum signal receiving means, for determining a status of the subsystem from the received spread spectrum data communications signal . 10. A communications system according to Claim 9 wherein the power bus comprises: a first plurality of conductors, positioned in the trailer; a second plurality of conductors, positioned in the tractor; and a connector which electrically connects the first plurality of conductors and the second plurality of conductors; and wherein said spread spectrum signal producing means is electrically connected to a conductor of said first plurality of conductors; and wherein said spread spectrum signal receiving means is electrically connected to a conductor of said second plurality of conductors. 11. A communication system according to Claim 10 wherein said connector comprises a SAE J560 seven-pin connector. 12. A communications system according to Claim 8, wherein said status determining means comprises: an indicator which indicates a staius of the subsystem to an operator positioned in the tractor. 13. A communications system according to Claim 12 wherein the tractor includes a cab having an instrument console positioned therein, and wherein said indicator comprises a display mounted on said instrument console. 14. A communications system according to Claim 12 wherein said indicator comprises at least one of an alphanumeric display, an a LED display, and an audio annunciator. 15. A communications system according to Claim 9, wherein said status determining means comprises: an indicator which indicates a status of the subsystem to an operator positioned in the tractor. 16. A communications system according to Claim 9, further comprising a tractor communications module housing, mounted to said trailer, which houses said spread spectrum signal receiving means and said indicator 17. A communications system for connecting to a combination of a tractor and a trailer mechanically and electrically connected to the tractor to communicate a command from the tractor to a subsystem positioned on the trailer, the system comprising: a power bus which supplies electrical power to the combination of the tractor and the trailer; spread spectrum signal producing means, positioned on the tractor and responsive to the subsystem, for producing a spread spectrum data communications signal representing the command on said power bus; and controlling means, positioned on the trailer, for controlling the subsystem based on the spread spectrum data communications signal . 18. A system according to Claim 17: wherein said spread spectrum signal producing means comprises means for producing said spread spectrum data communications signal from the command; and wherein said controlling means comprises: spread spectrum signal receiving means, positioned on the trailer and responsive to said power bus, for receiving said spread spectrum data communications signal; and means for controlling the subsystem from the received spread spectrum data communications signal . 19. A communications system according to Claim 17 wherein the power bus comprises: a first plurality of conductors, positioned in the trailer; a second plurality of conductors, positioned in the tractor; and a connector which electrically connects the first plurality of conductors and the second plurality of conductors; and wherein said spread spectrum signal producing means is electrically connected to a conductor of said second plurality of conductors; and wherein said spread spectrum signal receiving means is electrically connected to a conductor of said first plurality of conductors. 20. A communication system according to Claim 19 wherein said connector comprises a SAE J560 seven-pin connector. 21. A communications system according to Claim 17, further comprising operator input means for receiving a command from an operator positioned on the tractor, and wherein said spread spectrum signal producing means comprises means for producing a spread spectrum data communications signal representing the conveyed command. 22. A communications system according to Claim 21 wherein the tractor includes a cab having an instrument console positioned therein, and wherein said operator input means comprises a switch mounted on said instrument console. 23. A communications system according to Claim 17, further comprising operator input means for receiving a command from an operator positioned on the tractor, and wherein said spread spectrum signal producing means comprises means for producing a spread spectrum data communications signal representing the received command. 24. A communications system according to Claim 17, further comprising: a tractor communications module housing, mounted to said tractor, which houses said spread spectrum signal receiving means and said command receiving means. 25. A communications system for a combination of a tractor mechanically and electrically connected to a trailer, to communicate status and commands between the trailer and the tractor, the communications system comprising: a power bus which supplies electrical power to the combination of the tractor and the trailer; and bidirectional spread spectrum communicating means, responsive to a first subsystem on the trailer and to a command from the tractor to control a second subsystem on the trailer, for communicating a first spread spectrum data communications signal representing a status of the first subsystem from the trailer to the tractor and for communicating a second spread spectrum data communications signal representing a command to the second subsystem from the tractor to the trailer, said first and second spread spectrum data communications signals being superposed on said power bus. 26. A communications system according to Claim 25, wherein said first subsystem produces a status signal representing a status of the first subsystem, wherein said second subsystem receives a command signal which controls the second subsystem, and wherein said bidirectional spread spectrum communicating means comprises: first spread spectrum signal producing means, positioned on the trailer, electrically coupled to the power bus and responsive to the first subsystem, for producing said first spread spectrum data communications signal from the status signal; first spread spectrum signal receiving means, positioned on the trailer and responsive to the power bus, for receiving said second spread spectrum data communications signal; command signal producing means, responsive to said first spread spectrum signal receiving means, for producing the command signal to said second subsystem from the received second spread spectrum data communications signal; second spread spectrum signal producing means, positioned on the tractor and electrically coupled to the power bus, for producing said second spread spectrum data communications signal from a command; and second spread spectrum signal receiving means, positioned on the tractor and responsive to the power bus, for receiving said first spread spectrum data communications signal. 27. A communications system according to Claim 26, further comprising: a trailer communications module housing, mounted to said trailer, which houses said first spread spectrum signal producing means and said first spread spectrum signal receiving means; and a tractor communications module housing, mounted to said tractor, which houses said second spread spectrum signal receiving means and said second spread spectrum signal producing means. 28. A communications module for connecting to a trailer having a power bus for receiving power from a tractor mechanically and electrically connected to the trailer, the module comprising: a status signal input; a command signal output; spread spectrum signal producing means, responsive to said status signal input, for producing a spread spectrum data communications signal from a status signal provided at said status signal input; means for coupling said spread spectrum signal producing means to the power bus such that a spread spectrum data communications signal produced by said spread spectrum signal producing means is superposed on the power bus; spread spectrum signal receiving means for receiving a spread spectrum data communications signal and produces a command signal at said command signal output from the received spread spectrum data communications signal; means for electrically coupling said spread spectrum receiving means to a power bus such that a spread spectrum data communications signal superposed on the power bus is received by said spread spectrum signal receiver. 29. A communications module according to Claim 28, further comprising: a communications module housing which houses said spread spectrum signal receiving means and said spread spectrum signal producing means; and means for mounting said communications module housing to a trailer. 30. A communications module for connecting to a trailer having a power bus for receiving power from a tractor mechanically and electrically connected to the trailer, the module comprising: a status signal input; spread spectrum signal producing means, responsive to said status signal input, for producing a spread spectrum data communications signal from a status signal at said status signal input; means for coupling said spread spectrum signal producing means to the power bus such that a spread spectrum data communications signal produced by said spread spectrum transmitter is superposed on the power bus. 31. A communications module accor-ding to Claim 30, further comprising: a communications module housing which houses said spread spectrum signal producing means; and means for mounting said communications module housing to a trailer. 32. A communications module for connecting to a trailer having a power bus for receiving power from a tractor mechanically and electrically connected to the trailer, the module comprising: a command signal output; spread spectrum signal receiver for receiving a spread spectrum data communications signal and produces a command signal at said command signal output from the received spread spectrum data communications signal; means for electrically coupling said spread spectrum receiving means to the power bus such that a spread spectrum data communications signal superposed on the power bus is received by said spread spectrum signal receiver. 33. A communications module according to Claim 32, further comprising: a communications module housing which houses said spread spectrum receiving means; and means for mounting said communications module housing to a trailer. 34. A communications module for connecting to a tractor having a power bus which supplies electrical power to the tractor, the communications module comprising: a command input; spread spectrum signal producing means, responsive to said command input, for producing a spread spectrum data communications signal f:eom a command provided at said command input; means for coupling said spread spectrum signal producing means to the power bus such that a spread spectrum data communications signal produced by said spread spectrum signal producing means is superposed on the power bus; a spread spectrum receiving means for receiving a spread spectrum data communications signal; and means for electrically coupling said spread spectrum receiving means to the power bus such that a spread spectrum data communications signal superposed on the power bus is received by said spread spectrum signal receiver. 35. A communications module according to Claim 34, further comprising: a communications module housing which houses said spread spectrum signal producing means and said spread spectrum receiving means; and means for mounting said communications module housing on a tractor. 36. A communications module according to Claim 34 wherein the spread spectrum data communications signal superposed on the power bus represents a status of a subsystem, and further comprising status determining means, responsive to said spread spectrum receiving means, for determining a status of the subsystem from the received spread spectrum data communications signal. 37. A communications module according to Claim 36 wherein said status determining means comprises: an indicator which indicates a status of the subsystem; and means for mounting said indicator on the tractor such that the indicator is viewable by an operator positioned in the tractor. 38. A communications module according to Claim 36, further comprising: a communications module housing which houses said spread spectrum signal producing means, said spread spectrum receiving means and said indicator; and means for mounting said communications module housing on the tractor such that said indicator is viewable by an operator positioned on the tractor. 39. A communications module according to Claim 34, wherein said command input comprises: operator input means for receiving a command from an operator. 40. A communications module according to Claim 39, further comprising: a communications module housing which houses said spread spectrum signal producing means and said operator input means; and means for mounting said communications module on the tractor such that said operator input means is accessible to an operator positioned on the tractor. 41. A communications module for connecting to a tractor having a power bus which supplies electrical power to the tractor, the communications module comprising: a command input; spread spectrum signal producing means, responsive to said command input, for producing a spread spectrum data communications signal from a command provided at said command input; means for coupling said spread spectrum signal producing means to the power bus such that a spread spectrum data communications signal produced by said spread spectrum signal producing means is superposed on the power bus. 42. A communications module according to Claim 41, further comprising: a communications module housing which houses said spread spectrum signal producing means,- and means for mounting said communications module housing on a tractor. 43. A communications module according to Claim 41, wherein said command input comprises: operator input means for receiving a command from an operator. 44. A communications module according to Claim 43, further comprising: a communications module housing which houses said spread spectrum signal producing means and said operator input means; and means for mounting said communications module on the tractor such that said operator input means is accessible to an operator positioned on the tractor. 45. A communications module for connecting to a tractor having a power bus which supplies electrical power to the tractor, the communications module comprising: a spread spectrum receiving means for receiving a spread spectrum data communications signal; and means for electrically coupling said spread spectrum receiving means to the power bus such that a spread spectrum data communications signal superposed on the power bus is received by said spread spectrum signal receiver. 46. A communications module according to Claim 45, further comprising: a communications module housing which houses said spread spectrum receiving means; and means for mounting said communications module housing on a tractor. 47. A communications module according to Claim 45 wherein the spread spectrum data communications signal superposed on the power bus represents a status of a subsystem, and further comprising means, responsive to said spread spectrum receiving means, for determining a status of the subsystem from the received spread spectrum data communications signal. 48. A communications module according to Claim 47 wherein said status determining means comprises : an indicator which indicates a status of the subsystem to an operator. 49. A communications module according to Claim 48, further comprising: a communications module housing which houses said spread spectrum signal producing means, said spread spectrum receiving means and said indicator; and means for mounting said communications module housing on the tractor such that said indicator is viewable by an operator positioned on the tractor. 50. A method of monitoring an antilock braking system of a trailer having an antilock braking system for producing a data signal representing a status of the antilock braking system and a power bus which distributes electrical power to the trailer and a tractor connected thereto, the method comprising the steps of : producing a data communications signal from the data signal; communicating said data communications signal over the power bus; and determining a status of the antilock braking system from the communicated data communications signal . 51. A method according to Claim 50: wherein said step of communicating comprises the steps of : modulating the data communications signal to produce a spread spectrum data communications signal; and superposing the spread spectrum data communications signal on the power bus, at the trailer; and wherein said step of determining comprises the steps of: receiving the superposed spread spectrum data communications signal, at the tractor; determining a status of the antilock braking system from the received spread spectrum data communications signal. 52. A method according to Claim 50 wherein the step of determining comprises the step of indicating said status of said antilock braking system to a tractor/trailer operator positioned within a cab of a tractor connected to the trailer. 53. A method according to Claim 5JL wherein the step of determining comprises the step of indicating said status of said antilock braking system to a tractor/trailer operator positioned within a cab of a tractor connected to the trailer. 54. A method of communicating a status of a subsystem positioned on a trailer to a tractor electrically and mechanically connected to the trailer, the tractor and trailer combination including a power bus which supplies electrical power to the combination of the tractor and the trailer, the method comprising the steps of: producing a spread spectrum data communications signal representing a status of the subsystem on the power bus; and determining a status of the subsystem from the spread spectrum data communications signal. 55. A method according to Claim 54, wherein said step of determining comprises the step of: indicating a status of the subsystem to an operator positioned on the tractor. 56. A method of communicating a command from a tractor to a subsystem positioned on a trailer electrically and mechanically connected to the tractor, the tractor and trailer combination including a power bus which supplies electrical power to the tractor and the trailer, the method comprising the steps of : producing a spread spectrum data communications signal representing the command on the power bus; and controlling the subsystem based on the spread spectrum data communications signal . 57. A method according to Claim 5.6, wherein said step of communicating is preceded by the step of receiving a command from an operator positioned on the tractor. 58. A method according to Claim 56, wherein said step of controlling the subsystem comprises the step of : producing a command signal from the spread spectrum data communications signal .

Inventors: LESESKY ALAN C, WEANT BOBBY RAY, LESESKY, ALAN, C., WEANT, BOBBY, RAY
Applicants: LESESKY ALAN C, VEHICLE ENHANCEMENT SYSTEMS IN, WEANT BOBBY RAY, LESESKY, ALAN, C., VEHICLE ENHANCEMENT SYSTEMS, INC., WEANT, BOBBY, RAY
Application year: 1996
Main classification: B60R16
IPC codes: B60R16, G08G1