EP0541480B1 - Detektionsvorrichtung für Warendiebstahlsicherungsetiketten - Google Patents

Detektionsvorrichtung für Warendiebstahlsicherungsetiketten Download PDF

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Publication number
EP0541480B1
EP0541480B1 EP92810789A EP92810789A EP0541480B1 EP 0541480 B1 EP0541480 B1 EP 0541480B1 EP 92810789 A EP92810789 A EP 92810789A EP 92810789 A EP92810789 A EP 92810789A EP 0541480 B1 EP0541480 B1 EP 0541480B1
Authority
EP
European Patent Office
Prior art keywords
frequency
demodulator
signal
transmitting
generators
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92810789A
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German (de)
English (en)
French (fr)
Other versions
EP0541480A1 (de
Inventor
Burckart Kind
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Actron Entwicklungs AG
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Actron Entwicklungs AG
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Filing date
Publication date
Application filed by Actron Entwicklungs AG filed Critical Actron Entwicklungs AG
Publication of EP0541480A1 publication Critical patent/EP0541480A1/de
Application granted granted Critical
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Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
    • G08B13/2414—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using inductive tags
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2471—Antenna signal processing by receiver or emitter
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2477—Antenna or antenna activator circuit
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2488—Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver

Definitions

  • the present invention relates to a device for the detection of labels which are used for theft protection of goods and are provided with an electrical resonance circuit with a resonance frequency in the MHz range, the device comprising a plurality of pairs of transmit and receive antennas, each of which limits passages to be monitored , whereby each of the transmitting antennas of the pairs emits electromagnetic waves, the frequency of which is wobbled in wobble cycles over the predetermined resonance frequency of the labels, the wobble cycles of all pairs being synchronized with one another, and wherein a receiving circuit recognizing the presence of a label is sent to the receiving antenna of each pair connected.
  • the transmitting and receiving antennas are generally attached to the side of the cash register boxes, with, for example, a transmitting antenna attached to a first cash register box with a receiving antenna attached to the adjacent cash register box forms one of the pairs of transmitting and receiving antennas mentioned.
  • the radio frequency emitted via the transmission antennas is generated centrally in an HF generator and transmitted to the individual transmission antennas via correspondingly expensive radio frequency cables or fiber optic cables.
  • the cabling with the high-frequency cables or the fiber optic cables is quite complex.
  • the HF vibrations emitted as electromagnetic waves via the transmitting antennas are not generated centrally, but by decentralized first HF generators, each individually assigned to the transmitting antennas.
  • the wobble cycles are synchronized with one another using a synchronization signal supplied to the HF generators and generated in a central unit with at least one frequency that is different from the resonance frequency f R.
  • the decentralized HF generation advantageously eliminates the need for complex and very fault-prone cabling with the high-frequency lines or the fiber optic cables.
  • a signal with at least one frequency is generated centrally and transmitted to the individual HF generators.
  • the synchronization signal has a carrier oscillation onto which at least the desired fundamental frequency of the wobble cycles, but preferably additionally multiples of this fundamental frequency (e.g. 4 times and 32 times the basic frequency) is / are modulated.
  • the frequency of the carrier oscillation can then advantageously be used to determine the frequency of the wobble cycles and the frequency / s modulated onto the carrier oscillation after demodulation can be used to determine the phase of the wobble cycles.
  • the synchronization signal required for synchronization is simply fed into the electrical supply network, to which e.g. the cash registers are also connected.
  • the at least one frequency of the synchronization signal is in the long wave (LW) range.
  • LW signals on lines of an electrical building installation have a sufficient range for the present purpose.
  • the postal authorities of many countries have specifically released a frequency band for signal and data transmission via the electrical supply network in the LW area, which is advantageously used here.
  • a squarer is usually used at the input of the receiving circuits, in which the signal received by the receiving antennas is multiplied by itself. Label discrimination can be significantly improved if the received signal, which is subject to certain interferences, is multiplied by the pure RF oscillation supplied to the respective transmitting antenna instead of itself.
  • the HF generators can be connected not only to the transmitting antennas but also to the receiving circuits, which are connected to the associated receiving antennas. Again, this possibility advantageously arises without much Cabling effort as a result of the decentralized arrangement of the HF generators.
  • the transmitting antennas or receiving antennas are mounted laterally on a plurality of cash register boxes arranged in series, and the RF generators or receiving circuits assigned to them are spatially directly at them and thus on different sides of the passages between the transmitting and receiving antennas, which are delimited in each case the cash register boxes, in order to be able to connect the HF generators to the receiving circuits, HF lines would have to be laid crossing the passages between the transmitting antennas and their associated receiving antennas.
  • the RF vibrations respectively supplied to the receiving circuits for discriminating the label signals can be generated by specially provided, also decentralized, second RF generators individually assigned to the receiving circuits, also spatially.
  • these second RF generators must be synchronized with the first RF generators.
  • the synchronicity can be established very easily again using the synchronization signal which is preferably transmitted via the energy supply network and is already present in order to synchronize the first HF generators with one another.
  • the second HF generators can be integrated in a structural unit with the respective receiving circuits for which they are intended, and possibly also with the first HF generator for the transmitting antenna mounted on the same cash register.
  • This unit can advantageously be accommodated somewhere in the cash register box, for example.
  • the frequency of the signals emitted via the transmitting antennas is swept sinusoidally over the predetermined resonance frequency of the labels. Only the approximately linear sections of the wobble sine between the maxima and minima can be used for label detection, but not the time sections around its maxima and minima. However, these periods can be used sensibly, e.g. for the parallel deactivation of deactivatable labels. If the receiving circuits are deactivated or at least switched off during the deactivation during the above-mentioned periods of time, then undesired influences on the detection systems by the deactivation systems and thereby false alarms can also be avoided. The synchronism between the detection and deactivation units required for this can also be restored in a simple manner using the synchronization signal which is preferably available anyway on the power supply network.
  • the electromagnetic waves emitted by the transmitting antenna of each pair are wobbled in frequency-offset fashion with respect to the electromagnetic waves emitted by the transmitting antenna of each other pair, and that the receiving circuit of each pair is narrowband only at the respective transmitting frequency receiving the same antenna belonging to the same pair.
  • Fig. 1 shows two goods 20 provided with such resonance labels 21, for example.
  • antennas 8-13 are mounted on either side of the passages on the cash register boxes.
  • the antennas 8, 10 and 12 are transmitting antennas, the antennas 9, 11 and 13 receiving antennas.
  • the transmit antennas are controlled or fed by first RF generators 14-16, which generate RF vibrations with a frequency of approximately 8.2 MHz.
  • the frequency of 8.2 MHz which corresponds approximately to the target resonance frequency f R of the labels to be detected, is wobbled with a wobble frequency of approximately 85 Hz over a frequency range of a few hundred kHz (FIG. 2).
  • the wobble curves of the RF generators 14, 15 and 16 shown in Fig. 1 are denoted by 14 ', 15' and 16 '.
  • the individual wobble curves or wobble cycles and, of course, also the RF generators 14-16 that generate them and are arranged decentrally in the cash register boxes are synchronized with one another, as can also be seen from the wobble curves of FIG. 2.
  • a synchronization signal generated by a unit 22 and having a frequency or a frequency spectrum in the LW range is used for synchronization. This is coupled into a line 23 of the HF generators 14-16 and, inter alia, also the cash registers which supply electrical energy and is transmitted via this line to the elements mentioned.
  • Fig. 5 shows schematically the frequency spectrum of the synchronization signal in the LW range.
  • a dominant carrier frequency f 0 for example 145 kHz
  • the frequency f 1 (preferably 85 Hz) corresponds to the basic frequency of the wobble cycles of FIG. 2, and is therefore the wobble basic frequency.
  • the frequency spectrum of FIG. 5 is generated by modulating the frequency f 1 and 4 and preferably also 32 times f 1 onto a carrier oscillation with the frequency f 0 . 5 (arbitrarily) also shows the lower and upper range limits of the frequency band approved by post for data transmission on the electrical supply network and designated f B u and f B o , respectively.
  • PLL Phase Locked Loop
  • the secondary frequencies serve to produce the desired, matching phase position of the individual wobble curves.
  • FIG. 4 The block diagram of a preferred exemplary embodiment for such a synchronization circuit, which is assigned to one of the first RF generators (14-16), is shown in FIG. 4.
  • a central component of the synchronization circuit is a voltage-controlled oscillator (VCO) 32, which generates a clock frequency (of, for example, 48 MHz) as the mother frequency for the respective HF generator.
  • VCO voltage-controlled oscillator
  • the local carrier frequency f 0 and the local wobble base frequency f 1 are derived from the clock frequency of this VCO 32 by counters 33 and 34, which act as frequency dividers, and are coupled in a phase-locked manner or brought into phase with the corresponding signals generated in the central unit 22.
  • the modulated LW carrier oscillation for this is via a coupling transformer 29 and a downstream (broadband) LW amplifier 30 with automatic gain control (AGC) on the inputs of two identical, controllable Given demodulators D1 and D2, the internal structure of which is shown in FIG. 4.
  • the demodulators D1 and D2 perform a phase-sensitive rectification of the input signal relative to a control signal at the control input, which rectification will be explained later in connection with FIGS. 4 and 6.
  • As control signals for the two demodulators D1 and D2 two quadrature output signals (square-wave signals) of the local carrier frequency f 0 (140 kHz) from the first counter 33 are used.
  • the output signal of the first demodulator D1 is amplified in a subsequent amplifier 31, which preferably has a proportional / integral (PI) characteristic, and is used to control the VCO 32.
  • the blocks D1, 31, 32 and 33 thus form the PLL control loop already mentioned, which has the effect that the frequency and phase of the locally and centrally generated carrier oscillation are coupled equally or rigidly.
  • the output signal of the first demodulator D1 is approximately zero in the steady state of the control loop and the centrally generated carrier oscillation has a phase difference of +/- 90 ° from the control signal of the first demodulator D1.
  • the output signal of the second demodulator D2 is maximum because of the quadrature relationship between the control signals, ie it changes according to the envelope of the centrally generated, modulated carrier oscillation and thus represents the demodulated useful signal containing the frequencies f 1 , 4f 1 and 32f 1.
  • This Demodulation signal which contains the wobble frequency generated centrally in the unit 22, is now used to phase-lock the wobble frequency generated locally by means of the second counter 34.
  • a control loop is again used, which in its simplest configuration comprises a third demodulator D3, a downstream A / D converter 36, a microprocessor 35 and an adder 37.
  • the microprocessor 35 can be a module that is already used for other purposes and which additionally takes on the tasks shown here.
  • the second counter 34 has an output at which a word that is several (for example 16) bits wide is delivered and reaches a corresponding input of the adder 37; the same applies to the output of the adder 37.
  • the bit at the output with the highest weighting is designated in the adder 37 in FIG. 3 with MSB (Most Significant Bit), the one with the third largest weighting as MSB-2, the one with the sixth largest weighting as MSB-5.
  • MSB Mobile Bit
  • the locally generated wobble fundamental frequency is available through the MSB, the 2 2 th, ie, the 4th harmonic, and the MS 5-5 the 2 5 th, ie, the 32nd harmonic of the fundamental frequency.
  • the signal MSB from the output of the adder 37 serves as a control signal of the third demodulator D3.
  • the output signal of the second demodulator, ie the demodulated carrier oscillation serves as the input signal.
  • the output signal of the third demodulator D3 is not equal to zero.
  • This output signal is then converted in the subsequent A / D converter 36 into a digital value, which is further processed by the microprocessor 35.
  • the microprocessor 35 outputs an incremental number in accordance with the digital input value, which is added in the adder 37 to the numbers from the counter 34 and thus shifts the phase signal of the MSB output. This shift takes place in the control loop until the MSB signal and Demodulation signal have a fixed phase difference of +/- 90 °.
  • a fourth and fifth demodulator D4 or D5 are provided in parallel to the third demodulator, which receive the same input signal (demodulation signal), but as a control signal, the output signals MSB-2 or MSB-5 of the adder 37.
  • the outputs of the demodulators D3 to D5 can can be switched to the input of the A / D converter 36 selectively, in particular one after the other, by means of the switch shown schematically in FIG. 3.
  • phase of the MSB signal at the output of the adder 37 can be aligned in succession to the phase of the centrally generated wobble fundamental frequency in increasingly fine tuning.
  • the word that is phase-locked at the output of the adder 37 in this way to the centrally generated wobble fundamental frequency can be used accordingly in the associated HF generator.
  • a normal amplifier 38 and a reversing amplifier 39 are connected in parallel to the common signal input. Their outputs are connected to a common low-pass filter 42 via controllable, similar switches 40 and 41.
  • the first controllable switch 40 is controlled directly by the control signal present at the common control signal input, the second switch 41 via an inverter 43.
  • FIG. 6 The signals occurring in the circuit according to FIG. 4 are shown in FIG. 6: If a sine wave according to FIG. 6 (b) is present at the signal input of the demodulator Dn, it appears 6 (a) inverted at the output of the reversing amplifier 39, but normal at the output of the amplifier 38 according to FIG. 6 (b). If a square-wave signal of the same frequency but phase shifted by 180 ° is now applied to the common control input of the demodulator Dn according to FIG. 6 (c), both controllable switches 40, 41 are alternately opened and closed in such a way that at the input of the low-pass filter 42 sets the signal shown in Fig. 6 (e) which is characteristic of full wave rectification of the original sine signal.
  • the square-wave control signal - as shown in FIG. 6 (f) or (g) - is phase-shifted by 90 °
  • the signal shown in FIG. 6 (h) results at the input of the low-pass filter 42, which signal has the same positive and has negative voltage areas and therefore results in zero after averaging in the low-pass filter 42.
  • the case shown in FIG. 6 (a) - (e) is given for the second demodulator D2, the case shown in FIG. 6 (f) - (h) relates to the other demodulators D1 and D3, .., D5.
  • the phase position could also be set by "listening to each other" of the individual transmitter-receiver pairs, but this method is very complex to carry out, at least as long as the individual phases are still very different from one another.
  • the phase position has already been essentially set as desired by evaluating the above-mentioned secondary frequencies, a fine adjustment can advantageously also be carried out.
  • the resonance circles of these labels become vibrated by the electromagnetic waves emitted by the transmitting antennas excited. Most of the vibrational energy associated with this vibration is emitted again by the labels in the form of electromagnetic waves. In addition to those radiated directly from the transmitting antennas, these electromagnetic waves can also be received by means of the receiving antennas.
  • the receiving antennas are designed (for example, divided into two oppositely oriented sub-areas of the same size) in such a way that the majority of the radio frequency originating directly from the transmitting antennas is eliminated by self-extinction for far field suppression.
  • the receiving circuits 17 - 19 connected to the receiving antennas are used to discriminate the rather weak label signals from the high frequency still remaining, which comes directly from the transmitting antennas, and from background, etc. If successful, an alarm is triggered by the receiving circuit.
  • an analog multiplier or mixer (not shown) is located in the input area of the receiving circuits 17-19, among other things.
  • the signals originating from the receiving antennas are each multiplied by a high-frequency signal, which is generated by second RF generators provided for this purpose.
  • the second RF generators generate an RF oscillation which corresponds to that with which the transmitting antenna associated with the same pass is controlled on the other side of the pass.
  • the HF oscillation generated by the second HF generator 25 corresponds to that of the first HF generator 15.
  • the second HF generators can be synchronized with their associated first HF generators by means of the synchronization signal transmitted via the power supply line 23.
  • the sinusoidally selected wobble curves are slightly shifted against each other on the frequency axis, but their mutual frequency shift is so small compared to the frequency deviation (frequency amplitude of the wobble curves) that all wobble curves (including those of the others, outside) 1 section of localized first HF generators) still cut the target frequency f R with their approximately linear sections between their maxima and their minima.
  • all wobble curves not only intersect the target frequency f R but a certain frequency band f R +/- df around the target frequency in order to take into account manufacturing-related tolerances of the resonance frequency of the resonance labels.
  • the mutual frequency offset and the synchronism of the wobble curves ensure that the first HF generators generate different frequencies at any time. Since the receiving circuits 17-19 are designed such that they always receive sufficient narrowband only at the respective frequency of the first RF generator belonging to the same pass, a practically complete decoupling of the individual pairs of transmitting / receiving units is advantageously achieved.
  • FIG. 1, 26 and 27 also refer to deactivators arranged in the cash register boxes. These deactivators deactivate goods that have been properly paid for attached labels.
  • the deactivators can be synchronized with the receiving circuits 17-19 by means of the synchronization signal transmitted via line 23.
  • T D in FIG. 2 which in any case cannot be used for the discrimination of labels, while the deactivators are only active during these times, an excellent decoupling of the label detection and the label detection is also achieved. Deactivation reached.
  • the present invention is not restricted to the example explained, in which the transmitting and receiving antennas are mounted laterally on cash register boxes.
  • the antennas could just as well be free-standing directly at the exit and not installed in connection with cash register boxes.
  • the transmitting and receiving antennas arranged next to each other can even be designed like a single component.
  • a suitable geometric design of the antennas can also ensure that the reception via the receiving antennas by the. indirect proximity of the transmitting antennas is not affected too much.
  • the above-mentioned twisting of the receiving antennas is an example of this.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Burglar Alarm Systems (AREA)
EP92810789A 1991-10-31 1992-10-15 Detektionsvorrichtung für Warendiebstahlsicherungsetiketten Expired - Lifetime EP0541480B1 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
CH3185/91 1991-10-31
CH318591 1991-10-31
CH1098/92 1992-04-03
CH109892 1992-04-03
CH244692 1992-08-04
CH2446/92 1992-08-04

Publications (2)

Publication Number Publication Date
EP0541480A1 EP0541480A1 (de) 1993-05-12
EP0541480B1 true EP0541480B1 (de) 1996-07-24

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EP92810789A Expired - Lifetime EP0541480B1 (de) 1991-10-31 1992-10-15 Detektionsvorrichtung für Warendiebstahlsicherungsetiketten

Country Status (5)

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US (1) US5337040A (ja)
EP (1) EP0541480B1 (ja)
JP (1) JP2821068B2 (ja)
AT (1) ATE140813T1 (ja)
DE (1) DE59206809D1 (ja)

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Publication number Priority date Publication date Assignee Title
DE69321182T2 (de) * 1992-02-18 1999-04-08 Citizen Watch Co Ltd Datenträgersystem
US5610584A (en) * 1995-05-02 1997-03-11 Schrade; Chester R. Detection of goods on the bottom rack of a cart
US5874902A (en) * 1996-07-29 1999-02-23 International Business Machines Corporation Radio frequency identification transponder with electronic circuit enabling/disabling capability
DE19722078A1 (de) * 1997-05-27 1998-12-03 Meto International Gmbh System zur Überwachung von elektromagnetisch gesicherten Artikeln in mehreren Überwachungszonen
US5990791A (en) * 1997-10-22 1999-11-23 William B. Spargur Anti-theft detection system
EP1393445B1 (en) * 2001-02-08 2010-05-05 Sensormatic Electronics, LLC Automatic wireless synchronization of electronic article surveillance systems
US9201556B2 (en) 2006-11-08 2015-12-01 3M Innovative Properties Company Touch location sensing system and method employing sensor data fitting to a predefined curve
US8207944B2 (en) * 2006-12-19 2012-06-26 3M Innovative Properties Company Capacitance measuring circuit and method
US8040329B2 (en) 2006-12-20 2011-10-18 3M Innovative Properties Company Frequency control circuit for tuning a resonant circuit of an untethered device
US8134542B2 (en) 2006-12-20 2012-03-13 3M Innovative Properties Company Untethered stylus employing separate communication and power channels
US7956851B2 (en) * 2006-12-20 2011-06-07 3M Innovative Properties Company Self-tuning drive source employing input impedance phase detection
US8243049B2 (en) 2006-12-20 2012-08-14 3M Innovative Properties Company Untethered stylus employing low current power converter
US20080149401A1 (en) * 2006-12-20 2008-06-26 3M Innovative Properties Company Untethered stylus employing separate communication channels
US8040330B2 (en) * 2006-12-28 2011-10-18 3M Innovative Properties Company Untethered stylus empolying multiple reference frequency communication
US7787259B2 (en) * 2006-12-28 2010-08-31 3M Innovative Properties Company Magnetic shield for use in a location sensing system
US8089474B2 (en) * 2006-12-28 2012-01-03 3M Innovative Properties Company Location sensing system and method employing adaptive drive signal adjustment

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US4356477A (en) * 1980-09-30 1982-10-26 Jan Vandebult FM/AM Electronic security system
US4309697A (en) * 1980-10-02 1982-01-05 Sensormatic Electronics Corporation Magnetic surveillance system with odd-even harmonic and phase discrimination
US4623877A (en) * 1983-06-30 1986-11-18 Knogo Corporation Method and apparatus for detection of targets in an interrogation zone
DK161227C (da) * 1986-01-27 1991-11-25 Antonson Security Denmark Aps Apparat til synkronisering af tyveridetektorer
US4870391A (en) * 1988-04-05 1989-09-26 Knogo Corporation Multiple frequency theft detection system
NL9000186A (nl) * 1990-01-25 1991-08-16 Nedap Nv Deactiveerinrichting.

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Publication number Publication date
JP2821068B2 (ja) 1998-11-05
US5337040A (en) 1994-08-09
EP0541480A1 (de) 1993-05-12
DE59206809D1 (de) 1996-08-29
ATE140813T1 (de) 1996-08-15
JPH0620165A (ja) 1994-01-28

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