DE102005019098A1 - Certificate e.g. check, for use in e.g. central bank, has transponder provided with modulator to generate the modulated response signals based on stored identification data using modulated physical characteristics of readout signals - Google Patents

Abstract

The certificate has a radio frequency identification transponder (20) provided on a paper-like carrier unit. The transponder has a memory to store identification data of the certificate, and an antenna to receive readout signals and to transmit response signals modulated by a modulator. The modulator generates the modulated response signals based on the stored data using modulated physical characteristics of the readout signals. Independent claims are also included for the following: (1) a method for verifying authenticity of a certificate (2) a verification device for a certificate, comprising an antenna.

Description

The The invention relates to a bill, a check method for bills and a testing device for bills.

for Improvement of the counterfeit security of Can seem be provided in bank transponder. These transponders are arranged in or on the ticket and have data that a allow secure identification of the bill. As applications come For example, the authenticity check of Banknotes at banks (especially central banks) and the improvement and facilitating the authentication of Banknotes in shops, especially in shops retail, into consideration.

According to the state The technique may require a proof of authenticity Apparently done by encrypted Data of a transponder located in the ticket, e.g. RFID transponder, be read out. traditionally, allow this Data even the authentication of each individual transponder. This process is very complicated and expensive, as a corresponding high logic and memory power must be provided for it.

Of the The invention is based on the problem of a system for the authenticity of To provide a bill that is inexpensive to implement and a high counterfeit security offers.

The Problem is by a bill and by a check for bills solved with the features according to the independent claims.

One Bill has a paper-like carrier element and a transponder on, on and / or in the carrier element is arranged. The transponder also has a memory for Storing identification data of the bill, an antenna for receiving a read-out signal and for transmitting a modulated response signal, and a modulator for generating the modulated response signal the basis of the stored identification data by means of modulating physical properties of the response signal.

One Method of testing The genuineness of bills includes the steps of: sending a readout signal to a transponder connected to a ticket; Receive a modulated response signal of the transponder, wherein the response signal Has data that specifically modulates its physical properties are; and determining the authenticity of the bill based on the data and the specific modulation of the modulated response signal; and Issuing a test signal based on the specific authenticity of the note.

A Testing device for one Spark has an antenna for sending a readout signal and receiving a modulated response signal of one of the bills, wherein physical Characteristics of the response signal are modulated, and an evaluation circuit for testing the modulation of the response signal and for outputting a test signal based on the result of the test of the modulation of the response signal on.

Under A certificate is generally understood to be any document that is private Properly evidenced, whereby to the enforcement of the right the possession of the deed necessary is. For example, you can Securities (shares, unit certificates, warrants), bonds (Pfandbriefe, bearer bonds, medium-term notes, Convertible bonds, certificates u. a.), but also banknotes, checks, bills of exchange or insurance certificates be a semblance. This is the invention explained with reference to banknotes, although the invention with any kind of appearance is applicable.

A basic idea of the invention lies in the fact that physical properties of the response signal are modulated in an application-specific manner in order to achieve an improved forgery-proof of the bills. The physical properties mentioned are understood to be physical quantities which physically define the response signal, for example by means of telecommunications. In particular, the subcarrier frequency, the modulation depth or the phase modulation of the response signal can be varied during the transmission of the response signal. Furthermore, the number of subcarrier periods that code for a data bit can also be varied. Thus, not every transponder needs to be individually identifiable, but it can be used for all notes of a particular class similar transponders, each using its own modulation method. For example, transponders intended for bills of a particular denomination, eg 10 EUR banknotes, may use a special modulation, while the transponders intended for bills of another denomination, eg 50 EUR banknotes, use a different modulation. Such physically modulated response signals can not be emulated by conventional transponders. Since a mass production of similar transponders is thus possible, the manufacturing costs of these transponders can be kept small. The use of such transponders in It does not seem to make the costs of producing the bills expensive to an uneconomic extent.

Further can communication for consideration of the Authenticity of a note between a tester and a bill of the Test device designed become. Illustratively, this means that the modulation of the tester the read-out signal is given, and thereby the modulation of the Response signal of the transponder is influenced in the bill. This hardware side Design of the communication can not be influenced.

According to the invention is a Schein and a related Testing device created, the one quick, reliable and inexpensive Recognizing the authenticity of notes, e.g. Banknotes, allow.

Further is a test method for testing the authenticity of such a bill with a transponder according to the invention created.

During the Production of the note is the paper-like carrier element in the context of a papermaking process and a transponder is incorporated into the paper. The transponder can be covered with a protective cover beforehand. To the completion of the note, d. H. for example, the banknote, For example, the transponder can be used using the test method described above by means of high-frequency signals (HF) or ultra-high frequency signals (UHF) are read out. The application specific modulation of the Reply signal of the transponder improves the authenticity check of the Banknote.

There the transponder according to the invention For example, in the paper-like support member is included a sufficiently good isolation of the transponder from the environment allows.

preferred Further developments of the invention will become apparent from the dependent claims.

For example the modulator is arranged to transmit the response signal by means of a changed over time Subcarrier frequency to modulate, where the subcarrier frequency periodically or after sending a frame, also called as a frame, or after sending a given data pattern changed becomes.

The change the subcarrier frequency is a way to vary the modulation of the response signal. conventional Transponders are not capable the subcarrier frequency to change. The change the subcarrier frequency can be done automatically or triggered by the readout signal.

For example the modulator is arranged to transmit the response signal by means of a changed over time Modulation depth to modulate, where the modulation depth in time periodically, after sending a frame or after sending a changed given data pattern becomes.

The change the modulation depth is another possibility, the response signal to modulate, to the conventional Transponders are not capable. The change The modulation depth can also be done automatically here, or triggered by the readout signal become. The term "modulation depth" is the degree of on the carrier signal impressed Modulation understood.

For example the modulator is arranged to transmit the response signal by means of a To modulate variation of the phase modulation, the position, at which the phase modulation takes place, is varied. Especially The position at which the phase modulation takes place can be timed periodically, after sending a frame or after sending a preset one Data pattern changed become.

The change the phase modulation is another possibility, the response signal to modulate, to the conventional Transponders are not capable. The change the phase modulation can also be done automatically here, or triggered by the readout signal become. When changing In particular, the position is changed to the phase modulation which triggers the phase modulation becomes.

For example the modulator is arranged to transmit the response signal by means of a variable number of for a data bit encoding subcarrier periods to modulate, where the number of coding for a data bit Subcarrier periods changeable according to a given pattern is.

The change the number of subcarrier periods, the for encoding a data bit is another possibility, the response signal to modulate, to the conventional Transponder not capable are.

For example is the number of subcarrier periods, the for encode a data bit, about the same 8th.

Become significantly more than 8 subcarrier periods used to encode a data bit, this leads to longer data transfer times. In contrast, leads a lower number of periods than 8 to a difficult decoding, because the signal-to-noise ratio deteriorates.

For example is the number of subcarrier periods, the for One bit of data encodes the weight of the last one received Data bits dependent.

has the last received data bit e.g. a high level, so could then be a period number from 11 for encode a data bit while otherwise a period number of 7 is encoded for one data bit. Consequently There is no need to define and implement a global pattern.

For example the modulator is arranged to transmit the response signal by means of to modulate a combination of the above modulation types.

A Combination of different types of modulation allows further improvement the forgery security the modulated response signal and thus the note on which the Transponder is arranged.

For example the transponder is an RFID transponder.

RFID (Radio Frequency Identification) transponders are also used today already for different Task areas are used and allow the identification of various objects on which they are appropriate. In particular, the RFID transponders are not rely on their own power supply, as they use the energy of Readout signal for driving the circuits of the transponder and exploit to generate a response signal.

For example is the bill a banknote, an effects, a check or a Insurance policy.

For example is the response signal by means of a time-varying subcarrier frequency, a time-varying modulation depth, a varied phase modulation or a variable number of subcarrier periods that are for one data bit encode, modulate. For example, the modulation becomes periodic, after sending a frame or after sending a preset Data pattern changed. For example, the modulation may also vary between more than two states become.

conventional Transponders are not capable of that Modulate modulation. The change The modulation can be done automatically or by a read-out signal initiated become. In particular, the term "modulation depth" is understood to mean the degree of the carrier signal impressed Modulation. Clearly spoken of in the variation of the phase modulation changed the position at which the phase modulation takes place. The above mentioned modulation types of physical properties of the Response signal can in both the bill and the test apparatus for bills according to the invention be applied. Likewise, these types of modulation in the test method according to the invention to ensure an application-specific and tamper-proof Modulation of modulated response signals applied.

For example is the number of subcarrier periods, that in the method according to the invention for a data bit code, approximately equal to 8.

Become significantly more than 8 subcarrier periods used to encode a data bit, this leads to longer data transfer times. In contrast, leads a lower number of periods than 8 to a difficult decoding, because the signal-to-noise ratio deteriorates.

For example is the number of subcarrier periods, that in the method according to the invention for a data bit encode, depending on the significance of the last received data bit.

has the last received data bit e.g. a high level, so could then be a period number from 11 for encode a data bit while otherwise a period number of 7 is encoded for one data bit. Consequently There is no need to define and implement a global pattern.

For example the response signal is determined by a combination of modulation types according to the above modulated modulation types mentioned.

A Combination of different types of modulation allows further improvement the forgery security the modulated response signal and thus the note on which the Transponder is arranged.

For example has the testing device a memory, the data for the desired modulation of the modulated Response signal for comparison with the actual modulation of the modulated Response signal stores.

An advantage of providing a memory for the test apparatus is that data for the desired modulation can be stored therein. This data can be compared with the actual modulation, ie actual modulation, of the modulated response signal, so that the check for authenticity of the bill can be based on it. This makes it possible for the test device to send an arbitrary read-out signal to the ticket, and the application-specific modulated response signal in the test device is checked for whether this reply signal is modulated in accordance with the arbitrary read-out signal. In other words, the control of the communication is actively performed by the test apparatus while the trans Ponder reacts passively with the appropriate modulation of the response signal to the read-out signal of the test device. Thus, the counterfeit security of the bill can be further increased.

For example the test device has output means for visual or audible or electronic output of the result The examination on.

A Output by means such as a signal light and / or a Device for outputting a beep is a useful addition to the Testing device to improve the practicality of such a test device.

In summary is thus a forgery-proof Realization of a bill created. At the same time, the extra Costs by attaching a transponder to the bill arise, small, since the transponders due to mass production and can be produced without individual identifications.

A transponder according to the invention may for example have a thickness of 40 μm and a size of 0.1 mm ² , so that the transponder can be produced cost-effectively, since only a small amount of semiconductor area (eg of a silicon substrate) is required. The thickness of a bill may typically be 100μm.

embodiments The invention is illustrated in the figures and will be discussed below explained in more detail.

It demonstrate:

1 shows a bill having an RFID transponder according to an embodiment of the invention,

2 an RFID transponder according to an embodiment of the invention with some of its components,

3 a flowchart illustrating a method for checking the authenticity of notes according to an embodiment of the invention, and

4 a bill checking apparatus according to an embodiment of the invention.

Same or similar Components in different figures are given the same reference numerals Mistake.

The Representations in the figures are schematic and not to scale.

1 shows a glow 10 comprising an RFID transponder according to an embodiment of the invention.

The bill 10 , ie the banknote, has an RFID transponder 20 up in the glow 10 arranged, that is embedded in this, is. In particular, the RFID transponder 20 already in the making of the bill 10 arranged between two layers of paper. The exact position on the RFID transponder 20 in the bill 10 can be arranged substantially arbitrarily set. Due to the small size and the flat cross-section of the RFID transponder 20 he can in the glow 10 barely palpated with bare hands. In addition, the RFID transponder 20 thus protected from external influences. In particular, it is thus impossible to use the RFID transponder 20 inadvertently from the bill 10 replace, which would lead to the appearance 10 becomes worthless, as it would no longer be recognized as authentic by automated sham testers.

2 shows an RFID transponder with some of its components.

The RFID transponder 20 has a memory 23 for storing identification data of the bill 10 , an antenna 21 for receiving and transmitting signals and a modulating element 22 for generating a modulated response signal.

The memory 23 For example, it may have data that is the denomination of the bill 10 specify. Furthermore, in the memory 23 also the serial number of the bill 10 be stored if necessary. In addition to these data, it is above all also possible to store data which is necessary for the modulation of a response signal, ie information about which physical property of a response signal is to be changed when and in which way. These data are given by way of example only and may be stored in a real memory 23 be supplemented by further data, if necessary.

Furthermore, the RFID transponder has 20 an antenna 21 configured to receive a read-out signal and to send an application-specific modulated response signal. For the exact embodiment of the antenna 21 There are no other special requirements. In particular, the shape and size of the antenna 21 be adapted to the particular conditions under which it is used. For example, the antenna 21 be small, making them less easy by bending and folding the semblance 10 is damaged. Also the arrangement of the antenna 21 (and the RFID transponder DERS 20 ) in the bill 10 can be arbitrary. In particular, it may be advantageous to use the RFID transponder 20 to arrange near the metal strip and the antenna 21 to integrate into the metal strip. Alternatively, the RFID transponder 20 be integrated into any existing surveys of blind-writing on the banknote.

A component of the RFID transponder 20 However, according to the invention is a modulation element 22 adapted to receive a readout signal by means of the antenna 21 generate a modulated response signal and transmit it to the antenna for transmission. This is the modulation element 22 with the antenna 21 electrically connected. In addition, the modulation element 22 with the memory 23 electrically connected to the store 23 To read data stored in it. As already indicated above, the data can be both identification data of the bill 10 (eg, denomination and serial number, etc.) or modulation data indicating the exact manner of modulating the response signal.

In the following, a method for checking the authenticity of notes based on the 3 explained.

3 FIG. 10 is a flow chart illustrating a method of checking the authenticity of bills in a test apparatus.

In a first step is a read-out signal from a test device sent out (S10). This readout signal does not need any have special coding and / or modulation. However, that has to be Readout signal from an RFID transponder be interpretable.

This Readout signal is received by an antenna of the RFID transponder (S20). It is the antenna of the RFID transponder for picking up and transmitting the electrical energy of the vibrations of the readout signal to the other components of the RFID transponder set up so that no further power supply, such as a Battery, for the remaining Components of the RFID transponder is necessary.

The received read-out signal is transmitted from the antenna to the modulation element. By means of the modulation element, a response signal is generated, whose physical properties are specifically modulated (S30). The modulated response signal is based on those stored in memory Data and the modulation of the response signal may be in the memory stored data or depend on the readout signal.

If generates the modulated response signal from the modulation element it is transmitted to the antenna and transmitted from the antenna (S40).

This modulated response signal is then received by the tester and evaluated (S50). In particular, it checks to see if the special modulation corresponds to the modulation signal of the signal to determine whether the received signal is at all a signal from a valid Sham acts. Alternatively, the modulation of the response signal also checked whether it is the tested certificate for a EUR 10 note, a EUR 20 note or similar. is. That is possible if for every denomination the euro banknotes have a specific modulation of the response signal is provided. Is for each banknote provided the same special modulation, so can still be found out whether it was the examined Appearance for a valid Euro banknote is or not. In addition to the examination of Modulation of the bill also the signal content is read out and in the exam of Authenticity of the note included. For example, a bill would have its response signal the specific modulation of a EUR 100 bill and its data, the transmitted with the response signal but were displaying a EUR 10 bill obviously invalid.

In dependence from the above exam the modulation of the modulated response signal and the data of the Response signal becomes a test signal is output (S60) indicating whether the ticket is valid or invalid. This test signal can be output visually and / or acoustically.

in the Following are different options to the modulation of the response signal shown in detail.

According to a first embodiment, the response signal may comprise a time-varying subcarrier frequency. Conventionally, a constant subcarrier frequency is used, so that a conventional RFID transponder can be recognized as invalid by the tester if this RFID transponder does not execute a predetermined subcarrier frequency change. The change of the subcarrier frequency may, for example, be done periodically (ie after a predetermined number of subcarrier periods) or after the transmission of a complete frame. Alternatively, the change of the subcarrier frequency may also be changed in response to data sent by the readout signal. For example, two consecutive low levels of the readout signal may cause a change in subcarrier frequency. The subcarrier frequency may be between two subcarrier frequencies, such as 1/16 and 1/64 of the carrier frequency or, in principle, between several subcarrier frequencies. It will be appreciated that the counterfeit security of bills increases with the number of different subcarrier frequencies, but a higher number of subcarrier frequencies also requires a more elaborate and thus more expensive modulating element.

According to one second embodiment can the modulation depth can be changed over time. The modulation depth This indicates the degree to which the modulation of the carrier signal is varied. Circuit technology can realize the variation the depth of modulation through the use of various resistors which the applied antenna signal parallel to the transponder shorted according to the modulation sequence. It will a temporally changed Modulation depth generated when two or more resistors with known resistance value in alternating manner individually or simultaneously be used. The change the modulation depth can be as well as the change of the subcarrier frequency periodically (i.e., after a predetermined time), after transmission of a complete Frames or depending of data sent from the readout signal. Therefore, a re-description of the change in the modulation depth waived at this point and to the above mentioned corresponding Part of the description of the change of Subcarrier frequency directed.

According to one third embodiment changed the phase modulation. For example, the phase modulation can be changed thereby that phase jumps at different positions, e.g. with increasing or falling edge or between two edges. Another possibility is that the meaning of the phase jumps along a frame changes. The change the meaning of the phase jumps can e.g. according to a given pattern or depending from the transmitted data pattern. For example, two consecutive High level or low level cause such a change. Especially can be impressed on the carrier signal by means of Phasenumtastung a data signal, such that a modulated signal is formed, wherein the impressing of the data signal is performed between two adjacent edges of the carrier signal.

According to one fourth embodiment the number of subcarrier periods varies that for encode a data bit. traditionally, is the number of subcarrier periods, i.e. the word width for a data bit encoded, constant. For example, always encode 8 subcarrier periods a data bit. To increase the forgery security a bill, which has an RFID transponder according to the invention, can this number of subcarrier periods be varied. In particular, the number after a predetermined Patterns are varied. Vividly speaking, this means for Example, that first 9 subcarrier periods one data bit, the next one Data bit of 11 subcarrier periods coded and the subsequent data bits of 13, 7, 10, 9, 9, 12, 8 subcarrier periods etc. are encoded. Another possibility is that the word width depending on depends on the significance of the previously received data bit. For example could after a high bit, a period number of 11 subcarrier periods encode a data bit, after a low bit could have a period number of 7 subcarrier periods encode a data bit. An advantage of this procedure would be that no pattern needs to be given and implemented in the reader needs to be. In the variation of the period number of subcarrier periods, the one for one Coding data bits, care must be taken that the period number not much bigger than 8, otherwise data transfer times unnecessary extended be, and that the period number is not much smaller than 8 is because then the signal-to-noise ratio deteriorates, and the Decoding is difficult.

While so far the different embodiments for reasons the better representation only with in each case a varied physical Property, it is possible in principle, this various embodiments to combine to further increase the counterfeit security of bills to reach.

To the Example may be after a word width of 11 subcarrier periods the subcarrier frequency from 1/16 to 1/64 of the carrier frequency changed and after a word width of 8 subcarrier periods, the subcarrier frequency again from 1/64 to 1/16 of the carrier frequency reset become.

A other combined variations the physical properties can be, for example, that a change in the modulation mode (of phase shift keying (PSK, phase shift keying) to orthogonal phase shift keying (PSOK, phase shift orthongonal keying)) with a change in word width (e.g. 11 subcarrier periods at PSK and 8 subcarrier periods at PSOK) is, or the change the subcarrier frequency with the change linked to the modulation depth is.

As a general rule can all variations and combinations of the above individual embodiments come into use. A change in the one physical property can be used as a trigger for a change be used in another physical property.

4 represents a test device according to the invention for bills.

The test device according to the invention 30 for bills 10 has an antenna 31 , an evaluation circuit 32 , a store 33 and an output means 34 on.

The antenna 31 is arranged to send a read-out signal and to receive a response signal modulated by a ticket under test. The bill corresponds to the bill described above 10 In particular, the ticket is a transponder 20 and an antenna 21 for outputting a modulated response signal, wherein physical properties of the response signal are modulated.

Furthermore, the testing device 30 an evaluation circuit 32 on that with the antenna 31 the testing device 30 connected, and which is adapted to check the modulation of the response signal. Alternatively, the evaluation circuit 32 also evaluate the signal content, which can be coded.

The evaluation circuit 32 is also with an output means 34 as a signal light or an acoustic output device or an electronic interface connected to output the result of the test of the modulated response signal, ie to indicate whether the bill is valid or invalid.

The testing device 30 also has a memory 33 on that with the evaluation circuit 32 connected is. In the store 33 Data are stored for the desired modulation of the modulated response signal. These desired modulation data are in the evaluation circuit 32 compared with the actually received modulation data of the response signal of the bill, so as to determine the validity or invalidity of the bill. In the simplest case, the nominal modulation data indicate a fixed preset modulation pattern. In this case, each (valid) transponder 20 in response to the readout signal, output the same response signal, ie a similarly modulated response signal, the modulation of this response signal having to correspond to the modulation pattern that is present in the memory 33 the testing device 30 is stored. In a development, the stored data have rules from which it can be deduced with which modulation pattern the transponder 20 in the bill to be tested reacts to a transmitted readout signal. Clearly speaking, in this case, the modulation pattern of the modulated response signal is influenced by the readout signal. It is immediately obvious that this flexible approach increases the counterfeit security of the bills. In particular, the specification of the modulation method is on the side of the test apparatus 30 implemented.

common Feature of the bill, the test procedure and the testing device is that the way of modulating physical properties the read-out signal, i. the modulation method used and its modification via the Time, unauthorized third party is unknown.

10

bill

20

transponder

21

antenna

22

modulation element

23

Storage

30

Testing device

31

antenna

32

evaluation circuit

33

Storage

34

output means

S10

Send of the readout signal

S20

Receive of the readout signal

S30

Produce the modulated response signal

S40

Send the modulated response signal

S50

Receive and testing the modulated response signal

S60

Output the test result

Claims (31)

Shine with a paper-like carrier element; and a transponder on and / or in the carrier element, the transponder a memory for storing identification data of the bill; an antenna for receiving a readout signal and for transmitting a modulated response signal; and a modulator for generating the modulated response signal based on the stored Identification data by modulating physical properties of the read-out signal. Certificate according to claim 1, wherein the modulator is adapted to the response signal by means of a temporally changed Subcarrier frequency to modulate. Certificate according to claim 2, wherein the modulator is arranged to the subcarrier frequency periodically or after sending a frame or after to change the transmission of a given data pattern. A ticket according to claim 1, wherein the modulator is arranged to send the response signal by means of a modulate time-varying modulation depth. Certificate according to claim 4, wherein the modulator is arranged to the modulation depth periodically, after sending a frame or after Sending a given data pattern to change. Certificate according to claim 1, wherein the modulator is adapted to the response signal by means of to modulate a variation of the phase modulation. Certificate according to claim 6, wherein the modulator is adapted to the position at the the phase modulation is made to vary. Certificate according to claim 6, wherein the modulator is adapted to the position at the the phase modulation takes place, periodically, after the transmission a frame or after sending a given data pattern to change. Certificate according to claim 1, wherein the modulator is adapted to the response signal by means of a variable number of for a data bit encoding subcarrier periods to modulate. Certificate according to claim 9, wherein the modulator is adapted to count the number of bits of data coding subcarrier periods to change according to a given pattern. Certificate according to claim 10, where the number of subcarrier periods, the for encode a data bit, approximately is equal to 8. Certificate according to claim 9, where the number of subcarrier periods, the for One bit of data encodes the weight of the last one received Data bits dependent is. Certificate according to claim 1, wherein the modulator is adapted to the response signal by means of a combination of modulation types according to claims 2 to 5 to modulate. Certificate according to one of the preceding claims, wherein the transponder is an RFID transponder. Certificate according to one of the preceding claims, where the bill is a banknote, an effects, a check or a Insurance certificate is. Method of testing the authenticity of bills, which has the steps: Send a readout signal to a transponder, which with a note connected is; Receiving a response signal of the transponder, wherein the response signal has data whose physical properties are specifically modulated; and Determine the authenticity of the bill based on the data and the specific modulation of the response signal; and Issuing a test signal based on the specific authenticity of the note. Method according to claim 16, wherein the response signal by means of a temporally changed Subcarrier frequency is modulated. Method according to claim 17, where the subcarrier frequency periodically or after sending a frame or after is changed when sending a given data pattern. Method according to claim 16, wherein the response signal by means of a temporally changed Modulation depth is modulated. Method according to claim 19, where the modulation depth is temporally periodic or after transmission a frame or after sending a given data pattern changed becomes. Method according to claim 16, wherein the response signal by means of a variation of the phase modulation is modulated. Method according to claim 21, wherein the position at which the phase modulation is performed, is varied. Method according to claim 21, wherein the position at which the phase modulation takes place, periodically, after sending a frame or after sending a preset Data pattern changed becomes. Method according to claim 16, wherein the response signal by means of a variable number of for a data bit coding subcarrier periods is modulated. Method according to claim 24, where the number of for a data bit encoding subcarrier periods changed according to a given pattern. Method according to claim 25, wherein the number of subcarrier periods, the for a data bit approximately encode is equal to 8. Method according to claim 24, where the number of subcarrier periods, the for One data bit encodes the significance of the last received data bit dependent is. The method of claim 16, wherein said Response signal is modulated by means of a combination of modulation types according to claims 17 to 27. Testing device for bills according to claim 1, which has an antenna for transmitting a readout signal and receiving a modulated response signal of one of the bills, wherein physical properties of the response signal are modulated; and an evaluation circuit for checking the modulation of the response signal and outputting a test signal based on the result of the test of the modulation of the response signal. Testing device according to claim 29, wherein the testing device a Memory, the data for the desired modulation of the modulated response signal stores for comparison with the actual modulation of the modulated Response signal. Testing device according to claim 30, wherein the test device output means for visual or audible or electronic output of the result The examination on.