Trailer light monitor

A system which monitors the functioning of safety and signal light circuits on a trailer and verify the lights are operating properly. The system connects into the signal and safety light circuits of the trailer and includes a unit which can be positioned within view of an operator of the vehicle towing the trailer. The unit has an appropriate visual display which warns the operator if one of the safety or signal light circuits have ailed. The visual display can be light emitting diodes which provide an appropriate visual signal. The unit can also include an audio signaling device to warn of a failure in the signal and safety light circuit.

FIELD OF THE INVENTION
 The present invention relates to systems for monitoring the safety lighting
 circuits on a trailer. More particularly it relates to a system and
 apparatus for monitoring the safety lighting circuits on a trailer while
 the trailer is being towed.
 BACKGROUND OF THE INVENTION
 Trailers pulled by vehicles such as cars, trucks, sports utility or similar
 vehicles are extremely common. The trailers vary from open trailers for
 hauling loads to boat trailers and campers. One important requirement, for
 safety and legal reasons, is that the trailer have appropriate safety
 lights such as turn signals, brake lights, and running and parking lights.
 These lights naturally have to be controlled from the vehicle pulling the
 trailer so the driver can signal those behind the trailer of turns or
 braking actions before they occur or simply warn vehicles approaching the
 trailer from behind at night of the presence of the trailer being towed on
 the road. The trailer safety light circuits usually connect directly into
 the electrical system of the towing vehicle by standard connectors and
 wiring methods. The trailer safety light circuits generally work in tandem
 with the safety light circuits on the towing vehicle. However, the safety
 lighting circuitry of trailers have a notorious reputation for
 unreliability and failure. The inability of the vehicle operator to easily
 check to determine if the circuitry is operating properly only compounds
 this problem.
 Failure of the safety lighting circuits on a trailer can create extremely
 hazardous situations and the fact that the trailer being towed by the
 vehicle partially obstructs the `view` of the operator further compounds
 the problem. In order to verify the proper functioning of all of the
 safety lighting circuits the vehicle operator needs the assistance of a
 second party to stand behind the trailer to observe the operation of the
 safety lighting circuitry while the vehicle operator tests them. In
 addition to being an awkward method of verifying proper operation of the
 safety lighting circuitry it does not provide any suitable means to verify
 the proper functioning of the safety lighting circuitry during actual
 operation of the vehicle while towing the trailer. Additionally, the
 vehicle operator can not easily or conveniently test the safety lighting
 circuitry if he has no one present to assist in the process.
 Boat trailers present their own unique problems as a result of their being
 periodically submerged during the launching and retrieving of the boat
 which the trailer carries. The safety lighting circuits as a result of the
 periodic dunking have a tendency to corrode much more easily. Also, the
 circuit bulbs burn out much more frequently from being immersed in water,
 during the time they are `on` or activated, due to the vehicle operators
 inability to easily turn the circuits off.
 To further compound the problem, trailers tend to have a low maintenance
 priority and are often left outside exposed to the elements between use
 which in many instances can be infrequent
 SUMMARY
 It is an object of the present invention to provide an apparatus and system
 to allow a vehicle operator to quickly, test without the need for
 assistance from another, the safety lighting circuitry of a trailer when
 that trailer is connected to the vehicle with which the trailer will be
 towed.
 It is a further object of the present invention to provide an apparatus,
 system and method for the operator of a vehicle pulling a trailer to be
 able to periodically monitor the function of the trailer's safety light
 signal circuits and be able to determine when a failure occurs in those
 circuits.
 It is yet another object of the present invention to provide a system and
 apparatus which is easy and economical to manufacture and can be used in
 combination with most if not all trailer and vehicle electrical systems
 without any modification of those systems.
 The present invention accomplishes this and other objectives by providing a
 trailer light monitoring apparatus for monitoring the function of safety
 signal lights on a trailer during use of the trailer with a vehicle. The
 system has one or more monitoring circuits which can instantaneously
 detect variations beyond predefined parameters in one or more safety
 signal light circuits of a trailer during combined operation of the
 trailer with a vehicle. The system also has connectors to connect each of
 the monitoring circuits to one of the safety signal light circuits of the
 trailer and the vehicle electrical system. Each of the monitoring circuits
 also have a separate indicator attached to them. The indicators are
 positioned for observation by the vehicle operator during combined vehicle
 and trailer operation. The system functions such that when the monitoring
 circuit detects a malfunction of the safety light signal circuit which it
 monitors, the monitoring circuit signals the operator through the
 indicator to which it is attached.
 In a specific aspect the system of the present invention has three separate
 safety signal light circuits one for parking and running lights, one for a
 left turn/brake signal light and one for a right turn/brake signal light.
 Each of the safety signal light circuits have one monitoring circuit to
 monitor it. Each of the monitoring circuits has an indicator, a light
 emitting diode, attached to it which the monitoring circuit uses to signal
 variations beyond the predefined parameters.
 In a preferred embodiment actual monitoring only occurs when the vehicle
 operator activates the safety signal light circuits. Thus, if upon
 activation a safety signal light circuit is functioning properly the
 indicator sends a positive signal to the vehicle operator. On the other
 hand, if the monitoring circuit detects that the safety signal light
 circuit has malfunctioned it sends a negative signal to the vehicle
 operator. In its simplest form the indicator is an LED which turns on upon
 activation of the safety signal light circuit, if the safety signal light
 circuit is functioning properly. If the safety signal light circuit is not
 functioning properly, the LED does not turn on upon activation of the
 safety signal light circuit. The safety signal light circuits generally
 include turn signal circuits, a parking and running light circuit and a
 brake light circuit which usually consists of the left and right turn
 signal circuits operating together. In the case of the turn signal lights
 when functioning properly, the LED blinks in unison with the turn signal
 lights at the rear of the trailer. If the brake light circuit is
 functioning properly the LED's turn on every time the brake pedal is
 depressed and remain on for so long as the brake pedal is depressed
 indicating the brake lights on the rear of the trailer are turning on each
 time the brake pedal is depressed. Likewise when the parking and running
 lights are turned on and they are functioning properly the LED goes on and
 stays on for so long as the parking and running lights are functioning
 properly. On the other hand, if on activation of any of the safety signal
 light circuits they are not functioning properly, the monitoring circuit
 will so indicate by not turning on the appropriate LED at the time it
 should turn on.
 In another aspect of the present invention the monitoring circuit checks
 the current in the safety signal light circuit to determine if it has
 varied beyond predefined parameters.
 In yet another aspect of the present invention a meter can function as the
 indicator.
 The invention also provides a method for monitoring the safety signal light
 circuits of a trailer during operation of the trailer with a vehicle. The
 steps of the method include monitoring the electrical activity levels of
 one or more safety signal light circuits of a trailer during operation of
 the trailer with a towing vehicle; determining if during activation of the
 one or more safety signal light circuits whether or not the electrical
 activity levels meet predefined parameters; and indicating if the
 electrical activity levels meet the predefined parameters.
 In a further aspect of this invention the method of monitoring of
 electrical activity involves monitoring the current levels of the safety
 signal light circuits.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 As noted above the apparatus and system of the present invention provide a
 monitoring circuit or circuits which can warn the operator of a vehicle
 towing a trailer if the safety signal light circuits of trailer, such as:
 the running light circuit, turn signal circuits or brake light circuits
 have failed. Such failure can be total inoperability of the circuit or the
 blowing of one or more bulbs in the circuit etc. For example after
 connection of the apparatus and system of the present invention into the
 combined vehicle trailer electrical system the vehicle operator has on the
 dash 19 of FIG. 3 of the vehicle 20 of FIG. 1 a control and visual display
 unit 21. In its simplest form unit 21 has three LED's 24, 25 and 26 as
 well as a switch 22. The system allows the vehicle operator to then test
 the safety signal light circuits of the trailer.
 The system is designed, as will be described in detail below, to operate as
 follows: when the operator activates the left turn signal system of the
 vehicle the operator will see the left turn signal LED 24 blink in tandem
 with the left turn signal light of the vehicle indicating the left turn
 signal circuit of the trailer is functioning properly. Likewise when the
 vehicle operator activates the right turn signal of the vehicle, if the
 right turn signal circuit of the trailer is functioning correctly, the
 operator will see LED 26 blinking in tandem with the turn signal indicator
 of the vehicle. Similarly, when the operator turns on the vehicles running
 and parking light circuit, LED 25 will turn on and remain on until the
 lights of the vehicle are turned off or the parking and running light
 circuits of the trailer fail for whatever reason, such as a blown bulb or
 a break in the circuit etc. Finally, when the operator depresses the brake
 pedal of the vehicle activating the vehicle's brake lights, then LED's 24
 and 26 will light up in unison indicating that the brake light circuit of
 the trailer is operating correctly. Thus, as can be appreciated the system
 allows the vehicle operator to test the proper functioning of the trailer
 safety light circuits after connecting the trailer and vehicle but prior
 to using them together and to monitor them each time they are used during
 a trip.
 The preceding only provides a brief description of the overall function of
 the present invention in a preferred embodiment. After reviewing the
 following detailed description it will be come apparent that other
 arrangements exist which do not depart from the concept of the present
 invention.
 FIG. 1 provides an overall view of the present invention installed in an
 automobile 20 trailer 18 combination. The visual display control unit 21
 is positioned in the interior of the vehicle in a position where the
 driver can easily see it. FIG. 3 shows one such placement with the control
 and visual display unit 21 positioned on the dashboard 19 of the vehicle.
 Referring back to FIGS. 1 and 2 cable 36 connects the visual display unit
 21 to coupler 33. Coupler 33 in turn joins plug 31 to plug 32. Plugs 31
 and 32 are the standard four flat plugs well known in the industry and
 commonly used for the purpose of joining the electrical system of a
 trailer and a vehicle while the vehicle tows the trailer. Typically plug
 32 is the male plug and 31 is the female plug. Coupler 33 is then
 constructed to easily interconnect to plugs 31 and 32. Coupler 33 by
 interconnecting into the existing system of the trailer vehicle
 combination also conveniently integrates the monitoring circuitry of the
 present invention with the trailer safety signal light circuitry and the
 vehicle electrical system so that together the three operate as a unit.
 FIG. 2A provides an end view of male plug 32. In this type of set up prong
 30 provides the connection for ground, prong 28 connects the circuit for
 the left turn signal, prong 27 connects the circuit for the right turn
 signal and prong 29 connects the brake light circuit. Plug 31 connects to
 the vehicle electrical system in the standard fashion through cable 38 and
 plug 32 connects to the trailer electrical system in the standard fashion
 through cable 37. The connection of plugs 31 and 32 into the vehicle and
 trailer have not been included since it is well known in the art how they
 connect into the respective electrical systems. Also, although the present
 description only uses as an example an installation with a standard four
 flat connector those skilled in the art will readily know after reading
 the description the present invention can be used with any other type of
 plug configuration available and used to interconnect the electrical
 system of a trailer and a vehicle.
 FIG. 4 provides a block diagram of the overall functional elements of the
 system and how they interconnect to the trailer safety light circuitry and
 the vehicle electrical system. The remote or visual display 21 consists of
 light emitting diodes (LED's) 24, 25 and 26, as noted above in the
 preferred embodiment, positioned on the dash of the vehicle for the
 vehicle operator to see during operation of the vehicle. The visual
 display 21 connects to the monitoring and warning circuit 51, which will
 be described in detail below. The monitoring and warning circuit 51 which
 forms part of the monitoring apparatus of the present invention can be
 located in the control visual display unit 21 or in coupler 33. Switching
 unit 52 used in one version of the preferred embodiment is used to shut
 down the trailer light safety circuits. Connector 33 joins the trailer
 safety light circuits 54 to the vehicle electrical system 55 as well as
 switch unit 52 and the monitoring and warning circuit 51. The indicator
 can be a meter instead of an LED as depicted in FIG. 3A. In FIG. 3A the
 LED indicators 24, 25 and 26 are replaced by meters 24A, 25A and 26A. The
 meters operating as indicators would operate in the standard fashion.
 Thus, as depicted in FIG. 4, monitoring and warning circuitry 51, remote
 display 21, switch 52 and connector 33 form the monitoring system or
 apparatus of the present invention. The overall system works as follows,
 monitoring and warning circuit 51 monitors certain key parameters of the
 operation of the trailer safety light circuitry 54 for possible failure in
 the trailer safety signal light circuitry. The systems primary function as
 stated above is to warn the driver of a vehicle if any of the safety
 lights on the trailer under tow by that vehicle have failed. Such a
 situation can occur if the turn signal lights or brake lights burn out or
 a break in the line occurs. Upon an indication of a failure the monitoring
 and warning circuit signals a failure by means of the appropriate
 indicator on the visual display 21. In the preferred embodiment as
 indicated above, failure of a circuit or a signal light in that circuit is
 indicated by the appropriate LED on the visual display 21 or 21 not
 lighting on activation of the circuit which has the fault in it. Generally
 two types of failure can occur either an open circuit due to a blown bulb,
 break in the circuit etc., or a short circuit. However, given the typical
 circuitry found in trailers and vehicles a short circuit will quickly turn
 into an open circuit once the short circuit causes the standard fuse in
 the circuit to burn out or the circuit breaker in the circuit to open.
 Thus, the system of the present invention does not have to monitor for a
 short circuit since the short circuit if it persists will quickly turn
 into an open circuit as a result of a fuse blowing or a circuit breaker
 opening.
 The system of the present invention monitors the current and looks for a
 decrease in the current level as the key parameter for determining if
 there has been a failure in the safety light signal circuit. In its
 simplest form detection of an open circuit would indicate a failure.
 However, the typical safety light signal circuit such as a running light
 circuit or tail signal circuit on a trailer may have several lights and
 the failure of one would only cause a decrease in the current and not
 result in an open circuit. Thus, the preferred embodiment of the present
 invention monitors current levels and will react to specific drops in
 current levels as its key parameter or indicator. On the other hand the
 turn signal circuits may only have one bulb and if it blows an open
 circuit results. The system can be configured for each situation and in
 one embodiment described below addition of the appropriate device, a
 variable resistor, the vehicle driver can adjust the monitoring circuit to
 operate with the circuitry in each trailer and vehicle with which it is
 used.
 FIGS. 5 and 6 provide two slightly different versions of circuits which
 would function as the monitoring and warning circuits of the present
 invention. The only difference between the circuits being that in FIG. 5
 the mechanism 79 used to turn the trailer safety signal light circuits off
 is a standard type of relay controlled by switch 85, where as the
 mechanism 83 in FIG. 6 used to turn the circuit off is made up of
 transistors 83A, 83B and 83C which are controlled by a driver 84 which is
 in turn controlled by switch 85. Driver 84 functions as an amplifier and a
 transistor or similar device could be used. During immersion of a boat
 trailer in water to launch a boat or to retrieve it, being able to turn
 off all of the safety light signal circuits on a boat trailer eliminates
 the possibility of the safety light signal circuitry from shorting out and
 greatly reduces the possibility of the bursting of one or more bulbs in
 the safety light signal circuits.
 Comparators 72A, 72B and 72C form that part of the circuit in the preferred
 embodiment which senses the current drop and signals the failure of the
 particular safety lighting circuit which that comparator monitors. For
 example as seen in FIG. 6, comparator 72B in monitoring or comparator
 circuit 122 would sense a change in the current, specifically an open
 circuit or a current drop caused by a blown bulb in the circuit, as a
 result a drop of the load current or sense voltage which comparator
 detects across resistor 77. Resistor 77 is in the circuit of the left
 signal light circuit 92. Thus if one or more of the bulbs in this circuit
 blow or it becomes an open circuit with no current or in the event all
 bulbs in the circuit are blown, a corresponding drop in the load current
 or a complete loss of the load current occurs. Thus when the vehicle
 operator activates the left turn signal or depresses the brake pedal
 comparator 72B senses the change on its input lines 77A and 77B and its
 output does not go high as it normally would and consequently LED 71B to
 which comparator 73B attaches on line 102 does not light. Thus, the
 operator is instantaneously appraised of the fact a circuit failure has
 occurred which requires attention.
 Likewise comparators 72A and 72C operate, in their own respective
 comparator or monitoring circuits 121 and 123, in the same fashion as
 comparator 72B and its circuit 122 by detecting changes, i.e., decreases
 in the load current as sensed by voltage on resistors 76 and 78
 respectively. Resistor 76 being in the tail light and running light
 circuit and resistor 78 being in the right turn signal circuit. Thus when
 a bulb blows on the right turn signal circuit 93 comparator 72C senses the
 change caused by this event over it two inputs 78A and 78B. Comparator 72C
 then will not turn on LED 71C when the vehicle operator activates the
 right turn signal or the brake lights; thus, indicating a failure in the
 right turn signal circuit. In turn if a failure occurs in the running or
 tail light circuit 91 comparator 72A will not turn on LED 71A on
 activation of the running or tail lights and thus signal a failure in
 circuit 91.
 Standard practice in the industry generally configures the brake light
 circuit of a trailer in one of two ways. The most common arrangement uses
 both the left turn signal circuit 92 and the right turn signal circuit 93
 together as the brake light circuit. A less common method provides a
 wholly separate circuit for the brake lights. The design of the preferred
 embodiment of the present invention is designed for use with the more
 common method of using both the left and right turn signal circuits
 together as the brake light circuit. However, those skilled in the art
 will readily appreciate that the present invention can be easily designed
 to work with a trailer safety light system which has a separate brake
 light circuit.
 In the preferred embodiment, when the vehicle operator depresses the brake
 pedal both the left turn signal light 41A of FIG. 1 and right turn signal
 light 42A turn on and remain on for so long as the brake pedal is
 depressed. Additionally, if the brake light circuit is functioning
 properly the monitoring circuit 122 of the left turn signal circuit 92 and
 the monitoring circuit 123 of the right turn signal circuit 93 turn on
 LED's 71B and 71C. LED's 71B and 71C then remain on for so long as the
 brake pedal is depressed. If one of the turn signals is turned on when the
 brake pedal is depressed, the turn signal light activated to signal a turn
 will blink and likewise the respective LED will blink in unison. However,
 as can be easily appreciated, the driver will have no problem in
 determining if the system has malfunctioned since the LED would not light
 under any circumstances if the particular turn signal bulb had burned out
 or some other malfunction has occurred in the circuit.
 Many different types of schemes exist for placing lights on a trailer.
 Quite often the turn signal circuits only have one light in each of the
 turn signal circuits. The parking and running light circuits usually have
 two or more lights located at different positions on the trailer. FIG. 1
 depicts one of the simplest arrangements in use in which the left turn
 signal circuit has one light 41A and the right turn signal circuit has one
 light 42A. The parking and running light circuit has two lights 41B and
 42B. In FIG. 1 the left turn signal light 41A is combined, in a standard
 fashion, in one enclosure 41 with the parking and running light 41B and
 likewise the right turn signal light 42A is combined in one enclosure 42
 with the parking and running light 42B.
 An additional optional feature of each comparator or monitoring circuit
 121, 122 and 123 are rheostats or variable resistors 73, 74 and 75 on each
 of the comparator circuits. The rheostats allow the vehicle operator to
 tune the comparator circuits 121, 122 and 123 to the current
 characteristics of each trailer vehicle combination. The driver would
 adjust the rheostats to the point where the LED in each circuit turns on
 when that individual circuit is activated. At that threshold point just
 enough current flows through the respective safety circuit to activate the
 comparator to turn on the appropriate LED and any drop caused by a failure
 such as a blown bulb would result in enough of a drop in current so the
 respective comparator would not turn on the LED and thus warn the driver
 of the failure. The preceding only describes the preferred embodiment of
 the invention and those skilled in the art will readily appreciate that
 the comparator circuits can be set up in any number of different ways and
 still achieve the same result, a signal to the vehicle operator that a
 failure has occurred which creates a safety hazard and requires immediate
 attention. However, generally only the parking and running light circuits
 have more than one bulb. Consequently, on most applications only the
 parking and running light circuits would require a rheostat. The turn
 signal circuits generally only have one bulb and therefore a failure would
 result in an open circuit.
 In the simple arrangement depicted in FIG. 1 only the parking and running
 light monitoring circuit 121 of FIGS. 5, 6 and 7 needs a variable resistor
 73 since only the tail light or parking and running light circuit 91 have
 more than one bulb. Thus, as noted above, the sensitivity of monitoring
 circuit 121 can be adjusted to respond to one burned out bulb. Dial 39 of
 FIGS. 2 and 3 provides the driver of the vehicle with the means to adjust
 variable resistor 73 and thus control the sensitivity of monitoring
 circuit 121. The driver does this by turning on the parking and running
 lights and adjusting dial 39 until dial 39 reaches the point where the LED
 for the parking and running light circuit just turns on. At this point if
 just one of the bulbs in the parking and running light circuit should burn
 out, when the driver activates the parking and running light circuit the
 LED will not turn on and thus warn the driver of the problem. As
 previously noted, if the turn signal circuits only have one bulb, a device
 to adjust their sensitivity is generally not needed since the left and
 right turn signal circuits 92 and 93 would immediately have an open
 circuit if one of the bulbs burn out. In the event of an open circuit in
 the left turn signal circuit the monitoring circuit 122 for the left turn
 signal would not turn on LED 71B. Likewise the monitoring circuit 123 of
 the right turn signal circuit would not turn on LED 71C.
 The preferred embodiment of the present invention uses a National
 Semiconductor LM1946 Over/Under Limit Diagnostic Circuit 72 in FIGS. 5 and
 6. The LM1946 comes with five comparators 72A, 72B, 72C, 72G and 72H;
 thus, in the preferred embodiment only 72A, 72B and 72C are needed. 72G
 and 72H are not needed and thus grounded. However, those skilled in the
 art will readily appreciate that the appropriate comparator circuitry can
 be configured with a variety of readily available devices, other than the
 National Semiconductor LM1946, which devices can accomplish the tasks
 outlined above and that the invention is not limited by the examples
 depicted in FIGS. 5, 6 and 7. Also, discrete comparators could also be
 used configured in a number of different ways. Additionally, an
 appropriately configured operational amplifier could replace the
 comparators and the same results achieved.
 FIG. 7 provides another feature, an audio signal to backup the LEDs of the
 visual display. FIG. 7 is essentially the same circuit depicted in FIG. 6
 except three additional comparators have been added to the circuit 72D,
 72E and 72F, creating their own separate mini-circuit 124. These in turn
 connect to a standard buzzer 110. In the preferred embodiment the buzzer
 110 is isolated by diodes 103, 104 and 105. The negative inputs of
 comparators 72D, 72E and 72F as depicted in FIG. 7 attach respectively to
 the outputs of comparators 72A, 72B and 72C. The positive inputs of
 comparators 72D, 72E and 72F as depicted in FIG. 7 connect respectively to
 the tail light circuit, the left turn signal circuit and the right turn
 signal circuit. The comparators 72D, 72E and 72F work in a straight
 forward manner, for example if the operator of the vehicle activates the
 right turn signal if it operates correctly then comparator 72C activates
 LED 71C. Accordingly, comparator 72I senses activation of the right turn
 signal circuit 93 at its positive input and at the same time senses
 activation of LED 71C by comparator 72C. Therefore comparator 72F does not
 activate the buzzer 110. However, if there were a malfunction in the right
 turn signal circuit 93, i.e. a bulb blew, and comparator 72C in response
 does not activate LED 71C comparator 72F would sense comparator 72C's
 failure to activate LED 71C it would then activate buzzer 110 thus sending
 an audio signal alerting the vehicle operator of the failure. Comparators
 72D and 72E would operate in a like manner for the tail light circuit 91
 and left turn signals 92 respectively. In the preferred embodiment the
 buzzer would be located in the control visual display unit 21.
 Comparators 72D, 72E and 72F then provide 12 volt output if the current in
 their respective trailer safety circuits is below the required threshold.
 Output from any one of the LEDs' comparators 72A, 72B 72C circuits is
 sufficient to cause the comparator 72D, 72E or 72F to actuate the buzzer
 110. Buzzer 110 is a standard ceramic buzzer; however, any number of
 different types of buzzers currently available can be used. Additionally,
 in the preferred embodiment a number of additional circuit elements have
 been included in circuit 124 which include resistors 112, 113, 114, 115,
 116 and 117. Each of the positive inputs of comparators 72D, 72E and 72F
 also go to ground through resistors 115, 116 and 117 respectively.
 Those skilled in the art will readily appreciate the minor circuit elements
 in FIGS. 5, 6 and 7 are typical and thus a description of each circuit
 element in FIGS. 5, 6 and 7 has not been provided since those skilled in
 the art upon reading the description herein and studying the drawings will
 have no problem in understanding the invention and how it functions. Also,
 those skilled in the art will understand that most vehicle electrical
 systems operate on 12 volts and that the circuit elements have to be
 compatible with these systems.
 The preferred embodiment of the present invention depicted and described
 herein is configured for use in existing vehicles and trailers without any
 additional modifications other than installation of the standard
 connectors to the trailer and vehicle. However, it can be easily seen that
 the present invention can be adapted to new vehicle construction. It could
 be included as a trailer pulling package. The circuitry can be
 incorporated into that of the vehicle and the warning display or lights
 can be built into the dashboard of the vehicle or some other appropriate
 location. One such location could be on the front of the center rear brake
 light located inside the rear window of the vehicle. Thus when the driver
 looks in the rear view mirror he could check the warning lights or diodes.
 By building the entire system into a new vehicle with the trailer hook up
 connector included it would avoid the need for the disturbing of the
 vehicle electrical system and to add the standard trailer electrical
 hookup. All that the vehicle owner would have to do is purchase a trailer
 with the correct connector to link the vehicle electrical system to the
 trailer signal safety light system.
 While the invention has been particularly shown and described with
 reference to a preferred embodiment thereof, it will be understood by
 those skilled in the art that various changes in form and detail may be
 made to it without departing from the spirit and scope of the invention.