Track circuit and method for operating same

Abstract

The invention relates, inter alia, to a method for operating a track circuit (20) assigned to a track section (10) of a railway track system.According to the invention, information packets (IP) are formed using a base signal (BS), a control packet (KP) is formed for each information packet (IP), which control packet enables the associated information packet (IP) to be checked for correctness, the information packets (IP) with their control packets (KP) are fed into a first end of the track circuit (20), information packets (IP) received at a second end of the track circuit (20) and control packets (KP) received at the second end of the track circuit (20) are evaluated, the evaluation including checking whether the received control packets (KP) confirm the correctness of the received information packets (IP), and a decision is made on the basis of the evaluation result as to whether the track section (10) is to be regarded as occupied.

Description

[0001] The invention relates to a method for operating a track circuit associated with a track section of a railway track system. Track circuits are understood to be arrangements comprising a transmitting device for feeding a transmitted signal into a track section of a railway track system and at least one receiving device for receiving the transmitted signal to form a received signal and for generating a status indication describing the occupancy status of the track section.

[0002] The invention is based on the object of specifying a method for operating a track circuit which is easy to carry out and can also be carried out with track circuits of simple construction.

[0003] This object is achieved according to the invention by a method having the features according to claim 1. Advantageous embodiments of the method according to the invention are specified in subclaims.

[0004] According to the invention, information packets are formed using a base signal, a control packet is formed for each information packet, which enables the associated information packet to be checked for correctness, the information packets are fed in with their control packets at a first end of the track circuit, information packets received at a second end of the track circuit and control packets received at the second end of the track circuit are evaluated, the evaluation including checking whether the received control packets confirm the correctness of the received information packets, and a decision is made on the basis of the evaluation result as to whether the track section is regarded as occupied.

[0005] A key advantage of the method according to the invention is that the track circuit can be operated very safely and with minimal errors. This is because the receiving device can check, based on the evaluation of the control packets provided according to the invention, whether or not received signal sequences are suitable for determining the occupancy status of the track section. If, for example, a signal is coupled in by a device other than the transmitting device assigned to the track circuit, for example through crosstalk or through the coupling in of signals generated by the rail vehicle, and a superimposed signal is formed, this can be detected by the receiver, and the corresponding signals can be ignored.

[0006] A further significant advantage of the method according to the invention is that the operation of the track circuit can be carried out with a track circuit of simple construction, for example one without a direct signal connection between the transmitting device and the receiving device; because the verification of the correctness of the received signal can be carried out without a comparison with a reference signal transmitted via an additional direct signal connection.

[0007] It is considered advantageous if a random or pseudorandom sequence of bits is generated as the base signal, and the bits are used to generate bit packets that form the information packets or at least a component of the information packets. The base signal is preferably random or largely random to minimize the risk of incorrect signal interpretation; transmission signals with a low repetition frequency of one and the same signal pattern statistically increase the risk of a possible detection error.

[0008] The formation of the control packets preferably includes applying a mapping function to the information packets that maps a large input set to a smaller target set, forming mapping results, and adding the mapping results to the control packets.

[0009] The evaluation of the received control packets preferably includes re-applying the same mapping function to the received information packets to form control results and comparing the mapping results contained in the control packets with the control results.

[0010] The track section is preferably considered occupied if the control results deviate from the mapping results contained in the control packets by more than a predetermined amount, for example, if too few information packets are received over time for which the control results match the mapping results.

[0011] The formation of the control packets can, for example, include applying a CRC calculation to the information packets to generate CRC values ​​and adding the CRC values ​​to the control packets. The evaluation of the control packets can, for example, include applying the same CRC calculation to the received information packets to generate CRC control values ​​and comparing the CRC values ​​contained in the control packets with the CRC control values. For example, the track section can be considered occupied if the CRC control values ​​deviate from the CRC values ​​contained in the control packets by more than a predetermined amount, for example, if too few information packets are received over time for which the CRC control values ​​match the CRC values ​​contained in the control packets.

[0012] Alternatively or additionally, the generation of the control packets may include applying a hash calculation to the information packets, generating hash values, and adding the hash values ​​to the control packets. The evaluation of the control packets may include applying the same hash calculation to the received information packets again, generating hash control values, and comparing the hash values ​​contained in the control packets with the hash control values. For example, the track section may be considered occupied if the hash control values ​​deviate from the hash values ​​contained in the control packets by more than a predetermined amount, for example, if too few information packets are received over time where the hash values ​​contained in the control packets match the hash control values.

[0013] It is also advantageous if the formation of the control packets includes adding to each control packet a predefined identification information that identifies the track circuit, and disregarding those received control packets and their associated received information packets for which the predefined identification information is missing.

[0014] Alternatively or additionally, it can be advantageously provided that the formation of the control packets includes generating a signature for each control packet, which allows a check as to whether the control packet has been fed into the track circuit by the authorized transmitting device assigned to the track circuit, and disregarding those received control packets and their associated received information packets for which the specified signature is missing.

[0015] Alternatively or additionally, it can be advantageously provided that the formation of the information packets includes generating a signature for each information packet, which allows a check as to whether the respective information packet has been fed into the track circuit by an authorized transmitting device assigned to the track circuit, and disregarding those received information packets for which the specified signature is missing.

[0016] The track section is preferably considered occupied if no information packets are received or if too few information packets are received with corresponding control packets that confirm the correctness of the information packets.

[0017] The track section is preferably considered free if information packets with corresponding control packets confirming the correctness of the information packets are continuously received.

[0018] The method described above can also be applied to track circuits with multiple receiving devices or distributed receiving devices. Each individual receiving device preferably determines the status of its assigned subsection, forming a subsection-specific status information. By linking the subsection-specific status information, the status of the entire track section can then be determined, and a complete section-specific status information can be formed.

[0019] The invention also relates to a track circuit having a transmitting device for feeding a transmitted signal into a track section of a railway track system and at least one receiving device for receiving the transmitted signal to form a received signal and for generating a status indication describing the occupancy status of the track section.With regard to such a track circuit, the invention provides that the transmitting device is designed to form information packets using a base signal, to form a control packet for each information packet, which enables the associated information packet to be checked for correctness, and to feed the information packets with their control packets into the track circuit as the transmitted signal or as a component of the transmitted signal, and the receiving device is designed to evaluate received control packets, wherein the evaluation includes checking whether the received control packets confirm the correctness of associated received information packets, and to generate the status indication depending on the result of the evaluation of the control packets.

[0020] With regard to the advantages of the track circuit according to the invention, reference is made to the above explanations in connection with the method according to the invention and its advantageous embodiments.

[0021] The track circuit is preferably designed to carry out the methods described above.

[0022] The invention also relates to a transmitting device for a track circuit, in particular one as described above. According to the invention, the transmitting device comprises a computing device programmed to generate a base signal and, using the base signal, to generate the information packets and the corresponding control packets.

[0023] The track circuit is preferably designed to be used in a method for generating the transmission signal as described above.

[0024] The computing device is preferably programmed to generate a random sequence or pseudo-random sequence of bits as a base signal and to form bit packets with the bits as information packets, wherein the formation of the control packets includes applying a predetermined mapping function to the bit packets, which maps a large input quantity to a comparatively smaller target quantity, to form mapping results and adding the mapping results to the control packets.

[0025] The invention also relates to a receiving device for a track circuit, in particular one as described above. According to the invention, the receiving device comprises a computing device programmed to evaluate received information packets and received control packets. The evaluation includes checking whether the received control packets confirm the correctness of the received information packets and generating a status indication depending on the result of the evaluation of the control packets.

[0026] It is advantageous if the computing device is programmed to apply a predetermined mapping function to the received information packets to form control results, to compare mapping results contained in the received control packets with the control results and to regard a track section as occupied if the control results deviate from the mapping results contained in the control packets by more than a predetermined amount.

[0027] The invention is explained in more detail below using exemplary embodiments, which show, for example: Figure 1 shows a track section of a railway track system which is equipped with an embodiment of a track circuit according to the invention, wherein the track circuit according to Figure 1Embodiments of methods according to the invention are explained, Figure 2 shows an embodiment of a transmitting device which is suitable for the track circuit according to Figure 1 Figure 3 shows an embodiment of a receiving device which is suitable for the track circuit according to Figure 1 suitable and which can work together with the transmitting device according to Figure 2, Figure 4 shows a further embodiment of a device suitable for the track circuit according to Figure 1 suitable transmitting device, Figure 5 shows a further embodiment of a suitable transmitting device for the track circuit according to Figure 1 suitable receiving device which is compatible with the transmitting device in accordance Figure 4 can work together, and Figure 6 shows a further track section of a railway track system which is equipped with a further embodiment of a track circuit according to the invention.

[0028] For the sake of clarity, the same reference symbols are always used in the figures for identical or comparable components.

[0029] The Figure 1 shows a track section 10 of a railway track system, which is equipped with an exemplary embodiment of a track circuit 20 according to the invention. The track circuit 20 serves to monitor the track section 10 for its occupancy status and to generate a status indication ZA describing the occupancy status of the track section 10. Such a status indication ZA can, for example, lead to a Figure 1 signal box 30, which is only indicated schematically, in order to enable it to control the operation of the railway track system.

[0030] The track circuit 20 comprises a transmitting device 21 which is connected to rails 11 of the railway track system at one end of the track circuit 20 and serves to feed a transmitting signal S, for example in the form of a voltage signal U, into the track section 10.

[0031] The track circuit 20 also comprises at least one receiving device 22, which is connected to the rails 11 of the railway track system at another end of the track circuit 20 and serves to receive the transmission signal S from the transmission device 21 to form a reception signal E. Furthermore, the receiving device 22 checks the reception signal E for correct transmission of the transmission signal S or to determine whether the transmission signal S has been transmitted without corruption. The receiving device 22 assumes that in the case of an empty track section 10 or a track section 10 without an axle of a rail vehicle, the transmission of the transmission signal S should be largely interference-free, whereas in the case of an axle and an electrical short circuit or shunt or axle shunt between the two rails 11 caused by the axle, significant signal interference will occur.

[0032] In order to be able to detect such a signal disturbance particularly easily on the receiver side, it is possible to transmit the transmission signal S from the transmitting device 21 in parallel by means of a direct signal connection SV to the receiving device 22, as shown in the Figure 1 indicated by a dashed line.

[0033] The track circuit 20 according to Figure 1 does not require such a direct signal connection SV, since the receiving device 22 is designed to be able to evaluate the received signal E without additional knowledge of the transmitted signal S and to examine it for an axle-related signal disturbance. If the receiving device 22 detects a signal disturbance, it generates an occupied signal as status indication ZA, which indicates an occupied status of the track section 10. Otherwise, it generates a clear signal as status indication ZA, with which it signals the free or unoccupied status of the track section 10.

[0034] The Figure 2 shows in more detail a first embodiment of a transmitting device 21 according to the invention, which is used for the Figure 1 shown track circuit 20 and generates a transmission signal S, which enables the receiving device 22 to check the occupied state on the receiver side even without knowledge or without parallel transmission of the transmission signal S, i.e. without the Figure 1 indicated direct signal connection SV, enables.

[0035] The transmitting device 21 according to Figure 2 comprises a computing device 100, a memory 110 and a coupling device 120 for coupling the transmission signal S into the rails 11 of the track section 10.

[0036] In the memory 110, a computer program product CPP is stored which, when executed by the computing device 100, enables the computing device 100 to Figure 1 to generate the transmission signal S shown and to couple it into the rails 11 using the coupling device 120.

[0037] The computer program product CPP comprises in the embodiment according to Figure 1 a signal generation module SEM, which, when executed by the computing device 100, generates a base signal BS. The base signal BS can be a random sequence or pseudorandom sequence of bits, i.e., logical zeros and ones, or another random signal.

[0038] The signal generation module SEM is followed by a packet module PM, which divides the base signal BS into a sequence of information packets IP.

[0039] The packet module PM is followed by a transmitter-side mapping module ABB, which generates a control packet KP for each information packet IP of the packet module PM.

[0040] The information packets IP and the associated control packets KP reach a downstream combination module KOM, which forms an extended information packet IP with each information packet IP and the associated control packet KP, for example in the form of a data telegram DT.

[0041] The extended information packets IP or data telegrams DT are used as the transmission signal S according to Figure 1 forwarded by the computing device 100 to the coupling device 120, which feeds the transmission signal S into the rails 11 of the track section 10.

[0042] The operation of the transmitting device 21 is described below in accordance with Figure 2 illustrated in more detail using a concrete example.

[0043] The signal generation module SEM can generate, for example, a pseudorandom sequence of bits as the base signal BS, the first bits of which can look like this: BS = 0100111001000101010011001 …

[0044] The packet module PM receives the base signal BS or the bit sequence and divides it into a sequence F(IP) of information packets IP (IP1, IP2, ...), each of which can, for example, consist of 8 bits. The sequence F of information packets IP would thus look like this: F IP = IP 1 , IP 2 , IP 3 , … with IP1 = 01001110, IP2 = 01000101 and IP3 = 01001100

[0045] The sequence F(IP) of information packets IP reaches the transmitter-side mapping module ABB, which forms a control packet KP with each of the information packets IP.

[0046] To form the control packets KP, the mapping module ABB can, for example, apply a mapping function AF to the information packets IP, which maps a large input set to a comparatively smaller target set, thereby forming mapping results AE, and add the mapping results AE to the control packets KP or output them as control packets KP. In the latter case, the control packet KP1 would thus form the mapping result AE of the mapping function AF applied to the information packet IP1, the control packet KP2 would form the mapping result AE of the mapping function AF applied to the information packet IP2, and so on. The sequence F(KP) of control packets KP1, KP2, KP3, ..., or the sequence of mapping results AE, could, for example, look as follows: F KP = AE IP 1 , AE IP 2 , AE IP 3 , …

[0047] For example, the mapping module ABB can apply a hash calculation to each of the information packets IP, generating a hash value specific to the information packet and adding each hash value to the corresponding control packet KP. In such a case, the sequence F(KP) of control packets KP would, for example, look like this: KP 1 = HASH IP 1 = 01001110 , KP2 = HASH IP2 = 01000101 , KP3 = HASH IP3 = 01001100 … and F KP = HASH 01001110 , HASH 01000101 , HASH 01001100 … where HASH denotes the hash function used.

[0048] The sequence F(IP) of information packets IP and the sequence F(KP) of corresponding control packets KP are sent to the downstream combination module KOM, which assigns the corresponding control packet KP to each information packet IP. Each information packet IP and its corresponding control packet KP can, for example, be assigned to a data telegram DT; in such a case, the sequence of data telegrams DT forms the transmission signal S or at least a component of the transmission signal S. The transmission signal S can, for example, look like this: S = DT IP1 , KP1 , DT IP 2 , KP 2 , DT IP 3 , KP 3 , …

[0049] The Figure 3 shows in more detail a first embodiment of a receiving device 22 according to the invention, which is used for the Figure 1shown track circuit 20. The receiving device 22 has a computing device 200, a memory 210 and a decoupling device 220. The decoupling device 220 serves to decouple the transmission signal S received as reception signal E from the transmission device 21 according to Figure 1 from rails 11 of track section 10.

[0050] A computer program product CPP2 is stored in the memory 210, which programs the computing device 200 to evaluate information packets IP and received control packets KP contained in the received signal E and to generate the status information ZA depending on the result of the evaluation of the control packets KP.

[0051] In the embodiment according to Figure 3 The computer program product CPP2 comprises a readout module AUS, which uses the received signal E containing the data telegrams DT with E = DT IP1 ,KP1 , DT IP2 ,KP2 , DT IP3 ,KP3 , … reads the information packets IP and the control packets KP.

[0052] The information packets IP reach a receiver-side mapping module ABB arranged downstream of the readout module AUS, which can be identical to the mapping module ABB of the transmitting device 21 and subjects the incoming information packets IP to the same mapping function AF as the transmitter-side mapping module ABB of the transmitting device 21 did with the information packets IP in the context of generating the transmission signal S.

[0053] As part of the receiver-side implementation of the mapping function AF, the receiver-side mapping module ABB generates control results KE, which must be identical to the mapping results AE of the transmitter-side mapping module ABB if the received information packets IP match the information packets IP generated by the transmitter 21. If the received information packets IP differ from the information packets IP generated by the transmitter 21, then in the case of collision-free mapping, the control results KE will also differ from the received mapping results AE contained in the received control packets KP.

[0054] A comparison module VM, which is arranged downstream of the receiver-side mapping module ABB and the readout module AUS, compares the received mapping results AE with the self-generated control results KE; if the comparison module VM detects a discrepancy between the received mapping results AE and the self-generated control results KE, it concludes that the transmission is disturbed and discards the corresponding information packets IP.

[0055] The comparison module VM preferably considers the track section 10 to be occupied if no information packets IP are received, or if too few (too few per unit of time or too infrequently) information packets with corresponding control packets KP, which confirm the correctness of the information packets, are received beyond a predetermined level; in this case, the comparison module VM generates a status indication ZA, which indicates an occupied status or a possible occupied status of the track section 10.

[0056] The Figure 4shows in more detail a second embodiment of a transmitting device 21 according to the invention, which is used for the Figure 1 shown track circuit 20 can be used, and Figure 5 a matching second embodiment of a receiving device 22 according to the invention, which is connected to the transmitting device 21 according to Figure 4 can work together and also for the Figure 1 shown track circuit 20 can be used.

[0057] The transmitting device 21 according to Figure 4 includes in its computer program product CPP - compared to the computer program product CPP according to Figure 2 additional transmitter-side software modules that can reduce the risk that the track circuit 20 outputs an incorrect clear signal as the status indication ZA.

[0058] The receiving device 22 according to Figure 5includes a corresponding receiver-side software module for each of the additional transmitter-side software modules.

[0059] The transmitter-side software module marked with the reference symbol SI1 is a signature generation module which serves to form a transmitter signature SIG for each of the control packets KP generated at the transmitter side, based on which a corresponding receiver-side signature verification module ESI1 can check at the receiver side whether the control packets KP generated at the transmitter side actually originate from the transmitting device 21 or not.

[0060] The signature generation module SI1 can generate the signature, for example, using a private key of a key pair known only to the transmitting device 21; in such a case, the receiving-side signature verification module ESI1 can verify the signature using the corresponding public key of the key pair. If the signature verification is passed, the signature verification module ESI1 issues a confirmation signal OK and otherwise a warning signal NOK; if the signature verification is failed, the control packets KP and the associated information packets IP are discarded or considered not received.

[0061] The sender-side software module, marked with reference symbol SI2, is a signature generation module that generates a sender signature (SIG) for each of the IP information packets generated by the sender. The receiver-side software module, marked with reference symbol ESI2, is a signature verification module that performs a signature verification. If the signature verification fails, the associated IP information packets are discarded or considered not received.

[0062] The transmitter-side software module marked with the reference symbol SID is an identity transmission module that adds an identification ID to each data telegram DT generated by the transmitter, which identifies the transmitting device 21. The receiver-side software module marked with the reference symbol EID is an identity verification module that performs a corresponding verification of the received identification ID. If the identity verification fails, the associated information packets IP are discarded or considered not received.

[0063] The transmitting device 21 according to Figure 4 comprises in its computer program product CPP - compared to the computer program product CPP2 according to figure three further transmitter-side software modules and the receiving device 22 according to Figure 5Accordingly, it includes three additional transmitter-side software modules. Instead of all three of the shown pairs of additional software modules (SI1 / ESI1, SI2 / ESI2, and SID / EID), only a single pair can be provided, for example, the SI1 / ESI1 pair, the SI2 / ESI2 pair, or the SID / EID pair. Alternatively, only two of the aforementioned pairs can be present.

[0064] The Figure 6shows a track section 10 of a railway track system, in which a track circuit 20 has a transmitting device 21 and two receiving devices 22. The two receiving devices 22 each monitor the status of a sub-section assigned to them, forming a sub-section-related status indication TZA1 and TZA2; by linking the sub-section-related status indications TZA1 and TZA2 using an evaluation unit 23, the status of the entire track section 10 is determined and a complete section-related status indication ZA is formed. If one of the sub-section-related status indications TZA1 and / or TZA2 indicates an occupied status, a complete section-related status indication ZA is formed, which also indicates an occupied status; if all sub-section-related status indications TZA1 and TZA2 each indicate vacancy, a complete section-related status indication ZA is formed, which also indicates vacancy.

[0065] Finally, it should be mentioned that the features of all embodiments described above can be combined with each other in any way to form further other embodiments of the invention.

[0066] All features of subclaims can also be combined individually with each of the subordinate claims, either individually or in any combination with one or more other subclaims, in order to obtain further other embodiments.

[0067] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included. List of reference symbols

[0068] 10Track section 11Rails 20Track circuit 21Transmitter 22Receiver 23Evaluation unit 30Interlocking 100Computer 110Memory 120Coupling device 200Computer 210Memory 220Coupling device ABBMapping module AEMapping result AFMapping function AUSReadout module BSBase signal CPPComputer program product CPP2Computer program product DTData telegram EEceived signal EIDreceiver-side software module / identity verification module ESI1receiver-side signature verification module ESI2receiver-side software module / signature verification module FFequence IDIdentification information IPInformation packet KEControl result KOMCombination module KPControl packet NOKWarning signal OKConfirmation signal PMPacket module SSend signal SEMSignal generation module SI1transmitter-side software module / signature generation module SI2transmitter-side software module / signature generation module SIDtransmitter-side software module / identity transmission moduleSIGTransmitter signature SVSignal connection TZA1Subsection-related status information TZA2Subsection-related status information USVoltage signal VMComparison module ZAStatus information

Claims

1. Method for operating a track circuit (20) assigned to a track section (10) of a railway track system, characterized in that - information packets (IP) are formed using a base signal (BS), - a control packet (KP) is formed for each information packet (IP), which enables the associated information packet (IP) to be checked for correctness, - the information packets (IP) with their control packets (KP) are fed into a first end of the track circuit (20), - information packets (IP) received at a second end of the track circuit (20) and control packets (KP) received at the second end of the track circuit (20) are evaluated, wherein the evaluation includes checking whether the received control packets (KP) confirm the correctness of the received information packets (IP), and - a decision is made on the basis of the evaluation result as to whether the track section (10) is to be regarded as occupied.

2. Method according to claim 1, characterized in that a random sequence or pseudo-random sequence of bits is generated as a base signal (BS) and bit packets are generated with the bits, which form the information packets (IP) or at least a component of the information packets (IP).

3. Method according to one of the preceding claims, characterized in that- the formation of the control packets (KP) includes applying a mapping function (AF) to the information packets (IP), which maps a large input quantity to a smaller target quantity, to form mapping results (AE) and adding the mapping results (AE) to the control packets (KP), and - the evaluation of the received control packets (KP) includes reapplying the same mapping function (AF) to the received information packets (IP) to form control results (KE) and comparing the mapping results (AE) contained in the control packets (KP) with the control results (KE).

4. Method according to one of the preceding claims, characterized in that- the formation of the control packets (KP) includes applying a CRC calculation to the information packets (IP) to form CRC values ​​and adding the CRC values ​​to the control packets (KP), and - the evaluation of the control packets (KP) includes re-applying the same CRC calculation to the received information packets (IP) to form CRC control values ​​and comparing the CRC values ​​contained in the control packets (KP) with the CRC control values.

5. Method according to one of the preceding claims, characterized in that- the formation of the control packets (KP) includes applying a hash calculation to the information packets (IP) to form hash values ​​and adding the hash values ​​to the control packets (KP), and - the evaluation of the control packets (KP) includes applying the same hash calculation to the received information packets (IP) to form hash control values ​​and comparing the hash values ​​contained in the control packets (KP) with the hash control values.

6. Method according to one of the preceding claims, characterized in that - the formation of the control packets (KP) includes adding to each control packet (KP) a predetermined identification information (ID) which identifies the track circuit (20), and - those received control packets (KP) and their associated received information packets (IP) are disregarded for which the predetermined identification information (ID) is missing.

7. Method according to one of the preceding claims, characterized in that - the formation of the control packets (KP) includes generating a signature (SIG) for each control packet (KP), which signature allows a check as to whether the control packet (KP) has been fed into the track circuit (20) by an authorized transmitting device assigned to the track circuit (20), and - those received control packets (KP) and their associated received information packets (IP) are disregarded for which the predetermined signature (SIG) is missing.

8. Method according to one of the preceding claims, characterized in that- the formation of the information packets (IP) includes generating a signature (SIG) for each information packet (IP), which allows a check to be carried out as to whether the respective information packet (IP) has been fed into the track circuit (20) by an authorized transmitting device assigned to the track circuit (20), and - those received information packets (IP) which do not have the specified signature (SIG) are disregarded.

9. Method according to one of the preceding claims, characterized in that the track section (10) is considered occupied if no information packets (IP) with matching control packets (KP) confirming the correctness of the information packets (IP) are received or if too few information packets (IP) are received beyond a predetermined level.

10. Method according to one of the preceding claims, characterized in thatthe track section (10) is considered free if information packets (IP) with corresponding control packets (KP) confirming the correctness of the information packets (IP) are continuously received.

11. Track circuit (20) with - a transmitting device (21) for feeding a transmitted signal (S) into a track section (10) of a railway track system and - at least one receiving device (22) for receiving the transmitted signal (S) to form a received signal (E) and for generating a status indication (ZA) describing the occupancy status of the track section, characterized in that- the transmitting device (21) is designed to form information packets (IP) using a base signal (BS), to form a control packet (KP) for each information packet (IP), which control packet enables the associated information packet (IP) to be checked for correctness, and to feed the information packets (IP) with their control packets (KP) into the track circuit (20) as the transmitted signal (S) or as a component of the transmitted signal (S), and - the receiving device (22) is designed to evaluate received control packets (KP), the evaluation including checking whether the received control packets (KP) confirm the correctness of associated received information packets (IP), and to generate the status indication (ZA) depending on the result of the evaluation of the control packets (KP).

12. Transmitting device (21) for a track circuit (20), in particular a track circuit (20) according to claim 11, characterized in thatthe transmitting device (21) has a computing device (100) which is programmed to generate a base signal (BS) and to generate the information packets (IP) and the corresponding control packets (KP) with the base signal (BS).

13. Transmitting device (21) according to claim 12, characterized in that the computing device (100) is programmed to - generate a random sequence or pseudo-random sequence of bits as a base signal (BS) and - form bit packets with the bits as information packets (IP), - wherein the formation of the control packets (KP) includes applying a predetermined mapping function (AF) to the bit packets, which maps a large input quantity to a comparatively smaller target quantity, to form mapping results (AE) and adding the mapping results (AE) to the control packets (KP).

14. Receiving device (22) for a track circuit (20), in particular a track circuit (20) according to claim 11, characterized in thatthe receiving device (22) has a computing device (200) which is programmed to - evaluate received information packets (IP) and received control packets (KP), wherein the evaluation includes checking whether the received control packets (KP) confirm the correctness of the received information packets (IP), and - generate a status indication (ZA) depending on the result of the evaluation of the control packets (KP).

15. Receiving device (22) according to claim 14, characterized in thatthe computing device (200) is programmed to - apply a predetermined mapping function (AF) to the received information packets (IP) to form control results (KE), - compare mapping results (AE) contained in the received control packets (KP) with the control results (KE) and - regard a track section (10) as occupied if the control results (KE) deviate from the mapping results (AE) contained in the control packets (KP) by more than a predetermined amount.

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