DE102008044666A1 - Lights e.g. lamps, testing method for e.g. motor vehicle trailer, involves measuring comparison current value, and testing function of lights based on comparison of value of current flowing through lights with measured value - Google Patents

Abstract

The method involves monitoring current flowing through two lights (L1, L2) using a trailer controller (1) for actuating the lights depending on light signals of a motor vehicle. A comparison current value is measured by transmitting current pulses (I1, I2) for each light. Function of the lights is tested based on the comparison of value of current flowing through the lights with the measured comparison current value. The current is tested based on the measured comparison current value during single current impulse of lights. An independent claim is also included for a trailer controller comprising a signal input unit.

Description

The The invention relates to a method for checking lights of a vehicle trailer and a appropriately equipped trailer control. This is a through the trailer lights (lights the vehicle trailer) flowing electricity by means of a trailer control for operation the trailer lights dependent on monitored by light signals of the motor vehicle.

in the Frame usual Controls or failure indicators will be monitored on known trailer control units the lights are realized by a small current that flows in the lights, by detecting this current. This procedure is also under the term "open load detection "known. In a lighting channel in which only light emitting diodes (LED) as a luminous body are provided, this low current is not enough to the LEDs (LED) to turn on. This has the consequence that the lighting channel is interpreted as incorrect. For the evaluating electronics the luminaire channel appears as open and without consumer.

There LED illuminant not only in motor vehicle lights, but also in trailer lights increasingly Some of these LEDs are used in the LED luminaires Consumers in the form of a simple load resistance parallel to the LED's switched, a conventional incandescent to simulate corresponding load of about 21W. The by the light monitoring (open load detection) can then generate low power Resistance flow and simulates a properly functioning one Lamp. However, this has the consequence that either never an error can be detected in the light or additional electronics in the lamp must be accommodated, which contributes the load resistance Failure of one or more light emitting diodes in the LED lamp turns off.

moreover a lot of heat is generated at the load resistor and not one wasted little power. The additional monitoring electronics in the Luminaire itself means a much greater effort for the luminaire manufacturer and increased it Lights prices. Moreover, it is uneconomical, an electronic To develop a circuit, which is another electronic circuit bypasses itself to one usually by the other electronic Circuit to detect detected errors.

task The present invention is therefore a control or failure indication of trailer lights to propose that both light-emitting diodes and conventional lightbulbs or other luminaire body check in the vehicle trailer.

These The object is achieved with the features of claims 1 and 9. at The method described in the introduction is intended to be by Transmission of current pulses, which special test pulses or pulses during be able to operate, for every Lamp a comparison current value measured and the function of the lamp based on a comparison of the current value of the current flowing through the lamp is checked with the comparison current value. When the currents are different, is typically the lighting channel with the lower power rated as faulty, of course, certain Tolerances considered be that for the method is adjustable when comparing the different current values. In this procedure for checking the Luminaires by comparison with analog lamps in the pendant it is irrelevant which type of luminaire is used for the trailer lamp, since also the comparative current value for the luminaire is measured in each case becomes. Thus, the trailer control basically LED's, incandescent lamps or other luminaire body both in truck trailers as well as in motor vehicle trailers, which all differ in the recorded power and the flowing current, be used as it is equal by comparing two directly built-up lights on the light type does not arrive. An additional Electronics outside the trailer control is not necessary. In particular, on a 21W light can simulating load resistance in LED luminaires are dispensed with.

In An embodiment of the proposed method is at the same time Current pulses for two similar lights, in particular a left and / or right Lighting channel for a tail light, a brake light or the like., By the one lamp flowing Current selected as comparison current and compared with the current flowing through the other lamp. Especially So find a comparison between the left and the right light channel of the vehicle trailer instead of. During operation or by separate test pulses can so with every simultaneous operation the trailer lights a review take place since two corresponding lights are available to each recorded current or respectively recorded power to measure and to compare with each other. For Trailer turn signal lamps, except during operation when switching on a hazard warning lights are not operated simultaneously, Can this type of review in the context take place from separately generated test pulses, through which the left and right turn signal lights simultaneously actuated become.

in the Case of functioning lights is preferably a comparison current value stored, the simpler way from the mean of the two current values the parallel addressed lights can be formed to small Level out tolerances in the current consumption of functional luminaires. It is possible, the comparative values after each successful check of the function of the lamps or after certain time intervals to save, thus possible aging processes in the lights or a change the current consumption due to a caused by high stress warming automatically taken into account become.

Around a review of Trailer turn signals for each Luminaire type also possible during operation suggests one particularly preferred embodiment the invention that in addition with only one current pulse for a light a check of the flowing through the lamp Current based on a previously stored comparison current value done can, especially if the lights are light-emitting diodes, not without the emission of light signals by means of test pulses checked can be. The storage of the comparison current values can, for example, like previously described.

This is in the case of conventional Light bulbs as However, usually not necessary, as in this case sufficiently short test pulses can be generated as current pulses, a check of the connected light bulbs enable, without the lamps lighting up. Therefore, these can test pulses for example cyclically, d. H. after specified test intervals, or at certain test times, in the case of incandescent lamps connected to the respective lighting channels always be used and also during operation only one-channel switched lights by a parallel admission of each other corresponding lights with (not visible) test pulses tested simultaneously become. For the test pulses Therefore, a comparison current value is always present from a measurement.

in the Case of light-emitting diodes (LED) as a luminous element in the vehicle trailer is the situation is different. Due to the short switching times of the LEDs, it is not possible to create a light up the LEDs leading test pulses. Because during the However, do not drive the lights, not caused by the driver lights may be generated or should, in the case of LED's in one-sided control of a lamp, especially in the Frame of a turn signal monitoring, resorted to the comparison with stored comparative values become. It makes sense, if possible, to be saved Comparison current values in each case to current values of others, constructed analogously Lights used, in case of a longer lighting defect to avoid that a defective lamp is used, in the same Assume the comparison current value and the currently measured current value generated. In the case of turn signal lights is therefore as a comparison current value for the left turn signal lamp the current value of the right turn signal lamp and vice versa being used, of course Other embodiments of the invention are conceivable.

Around in a luminaire detection integrated in the process, whether incandescent or LED's as a lamp body in a lighting channel are connected, can according to the invention from the measured values of the current flowing through the luminaires a reference value be formed, which makes a distinction between LED's and incandescent allows. The reference value may in particular be the comparison current value, because a distinction of LED's and light bulbs can be taken by a different current consumption. Optionally, the reference value but also another from the Measured value, such as a response on the emission of a current pulse, a switching time or the like be. This reference value can easily be saved each time of the comparison current value for each channel, so that the trailer controls each current information about that gets whether in a lighting channel, an incandescent lamp or an LED connected as a lamp body is. Naturally the reference value can also be given by an input that is sent to the trailer control itself is made. In this case can be on a detection of LED's or incandescent lamps completely dispensed with according to the invention. As on a vehicle may also different vehicle trailers be coupled with the light bulbs or have LED's as a lamp body, However, it is according to the invention particularly advantageous, an automatic light detection based a reference value. The result of the luminaire detection can in the trailer control stored and used to determine whether regular test pulses can be generated on a lighting channel or whether pressing a Light for the implementation of a Measurement must be maintained. The first case is for a light bulb in the luminaire channel, the second case is to be applied to LEDs in the luminaire channel.

According to a preferred embodiment of the invention it is proposed, after connecting a vehicle trailer, at least one test pulse, in particular designed as a current pulse, preferably for each to be tested Lighting channel to produce, with two test pulses for comparable lights (tail light right and left, turn signals right and left, etc.) can be generated. This also applies in the case of LEDs, which are briefly flashed by the test pulse, which is not detrimental during the connection of the trailer. On the contrary, the lighting up of the trailer lights signal that an electrical connection has been made successfully and thus contributes to increasing the convenience of connection, as can be dispensed with a separate review of the switching functions of the individual lights by the driver. In a simple way, all luminaire channels can be controlled simultaneously. In the context of the invention, however, a sequential activation of two mutually correlated light channels is possible. According to the invention, the comparison current and / or reference value is determined during the test pulse during the connection of the vehicle trailer and a lamp recognition (LED or light bulb) is performed. In this case, it is not necessary to provide a complex storage of a comparison current or reference value when controlling only one light channel, which is technically relatively complicated and requires an increased demand for a plausibility check of the stored value.

in the Case of a review of a Lighting channel during operation and when only one control Lighting channel, d. H. especially when checking a turn signal, can provided according to the invention be, with a deviation of the measured current value of the previously Stored comparison current value to turn on another light. In particular, in case of an undetermined match the current value of a turn signal with the comparison current value the tail light on the same side of the vehicle with flashing. This generates on the one hand a meaningful replacement signal in the vehicle and thus increases traffic safety. On the other hand, this signal can be used to a trailer detection perform. in principle Of course, the above-described switching of another light is also possible possible, when a luminaire fails in a two-channel control. hereby a replacement signal is generated and at the same time the detection security elevated.

If namely the current value of the other luminaire with the possibly also separately for this Luminaire or the case of the control determined comparison current value matches, is an error signal for the original Light generated. Is also true for the other light does not match the signal, this indicates out there, that the trailer was decoupled. This is then communicated to the trailer control.

According to one preferred embodiment of the method is an error signal respectively for the lamp generated with the smaller current value. In the case of two parallel driven Thus, the fault signal is generated for the luminaire whose luminaire is illuminated Current value is smaller. This can be both the comparison current value as well as the measured current value. Both values will be the same time Measured on different, but corresponding lights, so that two equal current values are available. In the case individually controlled lights can apply accordingly. So can the comparison current value for the right turn signal, for example, measured from an operation for the left turn signal and saved. In a comparison of the comparison current value with the currently measured current value from a lighting or turn signal operation So also assumed that the lower current value comparable luminaires indicates a defect in the luminaire. This does not necessarily happen the currently measured value, but may also be be the comparison current value.

The The invention also relates to a trailer control for operation the light signals of a vehicle trailer with a signal input for receiving the light signals of a motor vehicle, both as Analog as well as bus signals can be received. There is also a signal output for preferably analog control of the lights of the motor vehicle trailer by Output of pulses provided. One trained in trailer control Computing unit is set up to control the lights respectively and to check the function of the lights. For this purpose, the arithmetic unit is set up according to the invention by the emission of current pulses in the form of test pulses or pulses during of current operations for each fixture to measure a comparative current value and the function the luminaire based on a comparison of the flowing current with the comparison current value to check. Especially is the processor and memory arithmetic unit for performing the above-described method or individually applicable parts submitted hereof.

Further Advantages, features and applications of the present Invention will become apparent from the following description of a embodiment and the drawing. In this case, all described and / or illustrated Features for itself or in any combination the subject matter of the present Invention, also independent from their summary in the claims or their back references.

It demonstrate:

1 a basic structure of a proposed circuit with a trailer control unit and two light channels;

2 various embodiments of the lamp body of a vehicle trailer as incandescent or light-emitting diodes (LED);

3 a flow diagram of the proposed method according to the invention and

4 a proposed inventions luminaire detection.

In 1 is schematically a trailer control 1 shown for actuating the light signals of a vehicle trailer. For this purpose, the trailer control 1 a signal input for receiving the light signals of a motor vehicle, which is formed in the present case as a bus signal input for receiving corresponding bus communication signals. These become an arithmetic unit 3 supplied, which evaluates the received signals and signal outputs 4 In the form of analogue connections, current pulses I ₁ and I _{2 are} emitted to lights L ₁ and L _{2 of} the vehicle trailer and lights L ₁ and L ₂ are illuminated.

The lights L ₁ and L ₂ may be a tail light, a brake light, a flashing light or the like. Light of the vehicle trailer, each lamp L ₁ , L ₂ via its own lighting channel 4 through the arithmetic unit 3 can be addressed.

To check the function of the lights L ₁ , L ₂ and possibly one in 1 not shown failure indicator is the arithmetic unit 3 set up in the signal outputs 4 flowing current I, which is generated by the current pulses I ₁ , I ₂ to measure. This can be done via shunt resistors on the signal outputs 4 be carried out, wherein the voltage drop across these shunt resistors to not shown in detail analog-to-digital converter connections (ADC ports) designed as a microprocessor computing unit 3 is read in and further processed and evaluated by means of data processing programs stored in the arithmetic unit.

The lights L ₁ , L ₂ may be as in 2 shown schematically to incandescent 5 or diode arrays 6 several parallel and / or series-connected LEDs 7 (LED) act.

An embodiment of the method proposed according to the invention is described below, in which many different process variants and steps are implemented simultaneously. According to the invention, the invention also relates to processes, each of which parts of in 3 relate and execute schematically explained method.

The proposed review of lights L ₁ , L _{2 of} a vehicle trailer is based essentially on the idea to measure a comparative current value I _VGL for each lamp L ₁ , L ₂ and the function of the lamp L ₁ , L ₂ based on a comparison of the current value of the by Luminaire current I to be tested with the comparison current value I _VGL . It is exploited in many parts of the proposed method according to the invention, that the lighting functions of a vehicle trailer are usually performed in duplicate, since usually for each lamp L ₁ , L _2, a right and a left light channel are formed.

To determine the defect of a lamp L ₁ , L ₂ can be used with simultaneously controlled lighting channels 4 on the right and left sides of the vehicle trailer the simultaneously measured current I through one lamp and the comparative current value I _VGL through the other lamp are used to determine if both lamps L ₁ , L ₂ are functioning properly. If the detected current values I, I _VGL differ, the respectively smaller current value I, I _VGL is assumed to be faulty.

The special feature of the proposed method is that it can be used for each type of luminaire in the lighting system of the vehicle trailer, since no absolute comparison with a specific current value I, but a relative comparison with a lamp L ₁ , L ₂ comparable type is proposed. Thus, the method and the inventively proposed trailer control, in which the method is implemented, both in trucks and passenger cars for LED's or incandescent lamps as a lamp body, without being limited to this lamp body.

Another point essential to the invention is that, in particular in the case of LEDs as lamps L ₁ , L _2, a measurement of the luminaire current I occurs when the signal is switched, since cyclic test pulses would be visible as current pulses I ₁ , I ₂ due to the short switching time of the LEDs and influence road users could.

Brake and taillight each have two light channels, which are actuated simultaneously by switching pulses and thus can be compared at the same time. Since the turn signal channels are switched separately, a comparison of the currently measured value with a previously stored value takes place according to the invention, the comparison preferably taking place in each case between the right and the left turn signal channel. Specifically, this means that upon actuation of the left turn signal, the current value I of the left turn signal channel is compared with a stored comparison current value I _{VGL of} the right turn signal channel.

Starting point for carrying out the method for checking the lights L ₁ , L _{2 of} a vehicle trailer in a trailer control 1 is the emission of a check pulse I _1, I ₂ and an actuation pulse I _1, I ₂ for turning on a lamp L _{1, L2.}

The actuating pulse represents a current pulse I ₁ , I ₂ , which is always generated when a light signal is to be operated in normal driving.

The test pulses I ₁ , I ₂ are usually short, fast current pulses that can be used in the case of incandescent bulbs as a luminous body to test the function of the light bulb without a lighting up of the incandescent lamps takes place. Due to the fast switching times of LED's as a luminous element, however, the test pulses lead to a short illumination of the driven LEDs and can therefore not be used for checking LEDs during the current driving operation. According to the invention, however, the test pulses can also be generated in the case of LEDs when connecting a trailer, for example, even all the light channels are controlled simultaneously to check their function. The lights can shine for a few seconds, and also signal to the driver of the vehicle that the connection of the trailer to the electrical system of the vehicle has worked.

Both the test pulses and the actuating pulses thus lead to the generation of a current pulse I ₁ , I ₂ for measuring the luminous flux, wherein a distinction is made between a single-channel drive and a two-channel drive.

In the two-channel control initially explained in detail below, two lighting channels are used 4 simultaneously activated. This occurs in normal operation, for example, in a brake light or tail light of the vehicle trailer. In the case of separate test pulses, this may also apply to the turn signal mode.

In the two-channel control so the left and the right light channel of the vehicle are controlled simultaneously, so that at the same time a current value I of the current flowing through a lamp L ₁ and a comparison current value I _VGL of the current flowing through the other lamp L ₂ both controlled lighting channels is available. In the context of the two-channel control, a direct comparison of the simultaneously measured current values I and I _{VGL takes place} . If both current values I, I _{VGL have} the value of 0A, this indicates that no trailer is connected. The trailer control in this case returns to the test mode in which cyclic test pulses are sent to perform the connection of a trailer and possibly a check of the incandescent lamps provided in the trailer.

In the case of a non-zero, but to the comparison current value I _VGL unequal current value I is for the lighting channel 4 with the lower current value I, I _VGL an error message is generated and returned to the test mode.

For the same current values I, I _VGL greater than 0A, a check is subsequently made as to whether in the lighting channel 4 a light bulb 5 or a diode array 6 with LEDs 7 is provided. If the check shows that no LED's are connected as a luminaire, the signal "luminaire OK" is output and returned to the test mode in which cyclic test pulses are performed for this luminaire channel to check the further function of the bulb.

If LED's are connected, the signal "Light OK" is also displayed, since the same as the current value I I was confirmed with the comparison current value I _VGL , which is the diode array 6 works.

After that, however, the trailer control does not return to the normal test mode, but switches for that lamp channel 4 in the actuation mode in which a review of the connected LED lights L ₁ , L ₂ takes place whenever this light L ₁ , L _{2 is operated} in the normal driving operation, to avoid that it by the test pulses to a unwanted lighting up the LED lamp comes.

Checking if a filament as an LED 7 or diode arrangement 6 or light bulb 5 is trained, as in 4 shown done.

For this purpose, first a comparison value for the lighting channel 4 stored in the case of a one-channel control of the lighting channel 4 can be used to determine whether the lamp L ₁ , L _{2 is} working properly.

In a two-channel drive, the comparison value I _{VGL can be} easily formed as an average of I and I _VGL . This should, except for small tolerances in the query of equality of the values I and I _VGL, each with and I _VGL to match. The actual test for the presence of a light bulb 5 or a diode array 6 is then performed by comparing the comparison _current value I _VGL with a threshold I _S.

In this case, therefore, the comparison _current value I _VGL simultaneously acts as a reference value I _REF , by means of which it can be decided whether an incandescent lamp is present in such a channel 5 or a diode array 6 connected. In the case of the measured current I, it can be checked whether the comparison current value I _{VGL is} greater than a threshold value I _S , which is an upper limit for the presence of LEDs 7 forms in the lamp body. If the comparison _current value I _VGL or the reference _current value I _REF exceeds this threshold value I _S , this is an incandescent lamp 5 connected. Otherwise, a diode array 6 connected. In trailer control 1 is stored, whether a light name 5 or an LED 6 in the lighting channel 4 connected.

The Saving this information can also be done depending on whether the Value already saved. For a stored value, the save step or the comparison with the threshold and an immediate Query done, whether for the lighting channel information "LED" or "light bulb" is stored.

For a two-channel drive, in the case of an actuation pulse (for LEDs or a test pulse for incandescent lamps), the interrogation is in each case as in relation to 3 described. However, it goes without saying for the person skilled in the art that the checking of the incandescent lamps can also take place within the scope of an actuating pulse. For this purpose, the trailer control starting from the test mode simultaneously switch to a combination mode, so that optionally an actuation pulse or a test pulse to check the bulbs 5 in a lighting channel leads.

In the case of a one-channel operation, it is first queried whether a comparison _current value I _{VGL has} already been stored. The storage can, for example, in the context of a test when connecting the vehicle trailer test pulse and the decision whether an LED 7 or diode arrangement 6 or a light bulb 5 are connected, done.

If this is not the case, a module for storing a comparison _current value I _{VGL is} triggered. This can be done in a variety of ways. For example, a comparison _current value I _VGL from typical values of the remaining lights L ₁ , L ₂ in the trailer assembly or an initial parameterization of the trailer, which can be recognized or interrogated, for example, when connecting the trailer, take place. It is also conceivable for the I _VGL memory module connected in the one-channel actuation case to remain in a wait state until the corresponding comparison value is automatically actuated in the context of a new actuation pulse. In the case of a comparison value I _VGL searched for the left turn signal channel, the I _VGL memory module can then wait until the right turn signal channel is actuated within the scope of an actuation pulse, which is then stored as the comparison current value I _VGL for the left turn signal channel. Also, in the case that only one lamp is provided in a non-doubly designed lamp channel, reference lamps for storing the comparison _current value I _{VGL can be} attracted. This can be done, for example, in the case of a rear fog light on the trailer, for which only a lighting channel is provided.

After saving the comparison value I _VGL or with already stored reference value I _VGL turn a query whether an LED 7 connected or not. This can be done analogously to the procedure in 4 take place, wherein the process step "I _VGL store" no longer needs to be performed. If no LED 7 is connected, the trailer control simply returns to its test mode and waits for the next test pulse to the incandescent lamp connected in this channel 5 to be checked by a suitable test pulse. In the case of an LED 7 the current value I in the switched lighting channel is determined and then a check is made as to whether the current value I matches the stored comparison current value I _VGL . If this is the case, the lamp is fine and the trailer control 1 returns to its actuation mode, awaiting the next actuation pulse.

If the measured current value I does not agree with the stored comparison current value I _VGL , it is proposed according to the invention to actuate another luminous element L ₂ , for example the tail light in the case of a defective turn signal. As a result, an alternative current value I _{ALT is} generated, which in turn can be compared with the comparison current value I _VGL , preferably using a comparison current value I _VGL provided for this light _channel and only auxiliary to the previously used comparison current value I _{VGL of} the light channel with the failed light L ₁ is used. If the alternative current value I _ALT coincides with the comparison current value I _VGL , this means that the alternative luminaire L ₂ functions properly if the luminaire channel 4 is controlled with the defective lamp L ₁ . In this case, an error output and a return to the actuation mode, in which the next actuation pulse for this luminous channel 4 is being serviced. If even if the alternative current value I _ALT does not match a comparison current value I _VGL , this indicates that no trailer is connected. In this case, the controller returns to its test mode where test pulses are periodically sent out to detect if a new trailer is being connected.

Within the scope of the invention, details of the method sequence, in particular in the context of LED detection or tag recognition, may be different. Essential for the present invention, however, is that in the case of LEDs 7 a check of the lights takes place during operation, so the LED's 7 do not light up by test pulses at unwanted times. It can be provided in the trailer bulbs 5 are also checked during the operation, unlike the diagram in accordance with 3 is shown.

1

trailer control

2

signal input

3

computer unit

4

Signal output, lights channel

5

light bulb

6

diode array

7

LED

I

Current value, current flowing through the lights

I _OLD

alternative current value

I _VGL

Compare current value

I _REF

reference value

I _S

threshold

I _1/2

current pulses

L _1/2

to shine

Claims (9)

Method for checking lights (L _1/2 ) of a vehicle trailer by monitoring a current (I) flowing through the lights (L _1/2 ) by means of a trailer control ( 1 ) for actuating the trailer lights (L _1/2 ) in response to light signals of the motor vehicle, characterized in that by transmitting current pulses (I _1/2 ) for each lamp (L _1/2 ) a comparison current value (I _VGL ) measured and the Function of the lamp (L _1/2 ) is checked by comparing the current value of the current (I) flowing through the lamp (L _1/2 ) with the comparative current value (I _VGL ). A method according to claim 1, characterized in that with simultaneous current pulses (I _1/2 ) for two similar lamps (L _1/2 ) of the one luminaire (L _1/2 ) current flowing as a comparison current value (I _VGL ) with the by the other lamp (L _1/2 ) flowing current (I) is compared. A method according to claim 1 or 2, characterized in that with only one current pulse (I _1/2 ) for a lamp (L _1/2 ), a check of the current (I) based on a previously stored comparison current value (I _VGL ). Method according to one of the preceding claims, characterized in that from the measured values of the current flowing through the luminaires (I), a reference value (I _REF ) is formed to determine in a luminaire detection, whether incandescent lamps or LEDs as lights (L _1/2 ) are connected. Method according to one of the preceding claims, characterized in that after connecting a vehicle trailer at least one test pulse is produced. Method according to one of claims 3 to 5, characterized in that in case of a deviation of the measured current value (I) from the previously stored comparison current value (I _VGL ) another light (L _1/2 ) is also connected. A method according to claim 6, characterized in that at a coincidence of the current value (I _ALT ) of the other lamp (L _1/2 ) with the comparison current value (I _VGL ) an error signal for the original lamp (L _1/2 ) is generated. Method according to one of the preceding claims, characterized in that an error signal for the lamp (L _1/2 ) with the smaller current value (I, I _VGL ) is generated. Trailer control for operating the lights (L _1/2 ) of a vehicle trailer with a signal input ( 2 ) for receiving the light signals of a motor vehicle and a signal output ( 4 ) for driving the trailer lights (L _1/2 ) by outputting pulses (I _1/2 ), and with a computing unit ( 3 ), which is adapted to the lights (L _1/2 ) to control and to check the function of the lights (L _1/2 ), characterized in that the arithmetic unit ( 3 ) is arranged to measure a comparative current value (I _VGL ) for each luminaire by emitting current pulses (I _1/2 ) and to determine the function of the luminaire (L _1/2 ) on the basis of a comparison of the flowing current (I) with the comparison current value ( I _VGL ).