U.S. patent application number 13/254532 was filed with the patent office on 2011-12-22 for device for detecting the occupied state and the free state of a track section as well as method for operating such a device.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Peer Bohlmann, Gerald Lude, Bernd Raschke.
Application Number | 20110309204 13/254532 |
Document ID | / |
Family ID | 42122783 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110309204 |
Kind Code |
A1 |
Bohlmann; Peer ; et
al. |
December 22, 2011 |
DEVICE FOR DETECTING THE OCCUPIED STATE AND THE FREE STATE OF A
TRACK SECTION AS WELL AS METHOD FOR OPERATING SUCH A DEVICE
Abstract
An apparatus for the detection of an occupied or free state of a
track section, which is particularly simple and at the same time
particularly resistant to interference influences, includes a
transmitter for feeding a transmitted signal, encoded by
modulation, into rails of the track section and at least one
receiver for receiving a received signal which is brought about by
transmission of the transmitted signal through the running rails of
the track section. The apparatus compares the modulation of the
received signal with the modulation of the transmitted signal. A
method for operation of an apparatus for detection of the occupied
and free state of a track section is also provided.
Inventors: |
Bohlmann; Peer;
(Schoenwalde, DE) ; Lude; Gerald; (Berlin, DE)
; Raschke; Bernd; (Berlin, DE) |
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
MUENCHEN
DE
|
Family ID: |
42122783 |
Appl. No.: |
13/254532 |
Filed: |
February 23, 2010 |
PCT Filed: |
February 23, 2010 |
PCT NO: |
PCT/EP2010/052247 |
371 Date: |
September 2, 2011 |
Current U.S.
Class: |
246/122R |
Current CPC
Class: |
B61L 1/188 20130101 |
Class at
Publication: |
246/122.R |
International
Class: |
B61L 1/18 20060101
B61L001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 2, 2009 |
DE |
10 2009 010 907.2 |
Claims
1-20. (canceled)
21. An apparatus for detection of an occupied or free state of a
track section having rails, the apparatus comprising: a transmitter
for feeding a transmitted signal, coded by modulation, into the
rails of the track section; and at least one receiver for receiving
a received signal produced by transmission of the transmitted
signal through the rails of the track section; the apparatus being
configured to compare the modulation on the received signal with
the modulation on the transmitted signal.
22. The apparatus according to claim 21, wherein the apparatus is
configured to produce the transmitted signal coded by any desired
modulation.
23. The apparatus according to claim 21, wherein the apparatus is
configured to produce the transmitted signal coded by random-number
based modulation.
24. The apparatus according to claim 21, wherein the apparatus is
configured to produce the transmitted signal coded by frequency
modulation.
25. The apparatus according to claim 21, wherein the apparatus is
configured to produce the transmitted signal coded by bit sequence
modulation.
26. The apparatus according to claim 25, wherein the apparatus is
configured for bit-by-bit comparison of the modulation on the
received signal with the modulation on the transmitted signal.
27. The apparatus according to claim 21, wherein the apparatus is
configured for continuous coding of the transmitted signal.
28. The apparatus according to claim 21, wherein the apparatus is
configured to compare, in a manner being safe from a signaling
point of view, the modulation on the received signal with the
modulation on the transmitted signal.
29. The apparatus according to claim 21, wherein the apparatus is
configured to produce a fault signal indicating a disturbance
state, based on the comparison of the modulation on the received
signal with the modulation on the transmitted signal.
30. The apparatus according to claim 29, wherein the apparatus is
configured to output the fault signal as at least one of a visual
or audible warning signal.
31. The apparatus according to claim 21, wherein the apparatus is
configured to transmit data signals through the rails of the track
section to a rail vehicle occupying the track section.
32. A method for operation of an apparatus for detection of an
occupied or free state of a track section having rails, the method
comprising the following steps: feeding a transmitted signal, coded
by modulation, into the rails of the track section; receiving a
received signal resulting from transmission of the transmitted
signal through the rails of the track section; and comparing the
modulation on the received signal with the modulation on the
transmitted signal.
33. The method according to claim 32, which further comprises
coding the transmitted signal by any desired modulation.
34. The method according to claim 32, which further comprises
coding the transmitted signal by random-number based
modulation.
35. The method according to claim 32, which further comprises
coding the transmitted signal by frequency modulation.
36. The method according to claim 32, which further comprises
coding the transmitted signal by bit sequence modulation.
37. The method according to claim 36, which further comprises
comparing the modulation on the received signal bit-by-bit with the
modulation on the transmitted signal.
38. The method according to claim 32, which further comprises
coding the transmitted signal continuously.
39. The method according to claim 32, which further comprises
comparing the modulation on the received signal, in a manner being
safe from a signaling point of view, with the modulation on the
transmitted signal.
40. The method according to claim 32, which further comprises
producing a fault signal indicating a disturbance state, based on
the comparison of the modulation on the received signal with the
modulation on the transmitted signal.
41. The method according to claim 40, which further comprises
outputting the fault signal as at least one of a visual or audible
warning signal.
42. The method according to claim 32, which further comprises
transmitting data signals through the rails of the track section to
a rail vehicle occupying the track section.
Description
[0001] The present invention relates to an apparatus for detection
of the occupied or free state of a track section having a
transmitter for feeding a transmitted signal which is coded by
means of modulation, into the rails of the track section and at
least one receiver for receiving a received signal which is
produced by transmission of the transmitted signal via the rails of
the track section.
[0002] One such apparatus is known in the form of a track free
signaling device, in the form of a track circuit, for example from
the company publication from Siemens AG "FTG S--Gleisfreimeldung
mit dem Tonfrequenz-Gleisstromkreis FTG S" [FTG S--Track free
signaling using the FTG S audio-frequency track circuit], Order No.
A19100-V100-B607-V2. In this case, the transmitter feeds an AC
voltage into the rails of a track section to be monitored. A
receiver receives a received signal in the form of the incoming
voltage, and evaluates the received signal. Since a short circuit
is produced between the rails of the track section by the axles of
a rail vehicle which is traveling on the track section, this
prevents the transmitted signal from being transmitted to the
receiver. This therefore makes it possible to identify that the
relevant track section is occupied.
[0003] In order to improve the reliability against disturbance
influences and in particular to make the track circuit insensitive
to electrical influences caused by harmonics in the track return
current, the transmitted signal is coded by means of modulation in
the known apparatus.
[0004] In this case, one of a total of 15 available, fixed
predetermined bit patterns of different length for each track
circuit frequency is modulated as coding onto the transmitted
signal. At the receiver end, the coding is read in the form of the
modulation from the received signal and is compared with the fixed
predetermined coding for the respective track circuit. This ensures
an unambiguous and correct association such that a received signal
received by the receiver also actually originated from the
transmitter for the same track circuit. This precludes the
possibility of a received signal from a different track circuit
incorrectly being received, for example because of electrical
influences, for instance by the conductors in two lines which are
carried in one cable touching, and being used for the detection of
the occupied or free state of the track section.
[0005] The known apparatus has the disadvantage that only 15 bit
patterns are available for coding. When using an audio-frequency
track circuit with transmitted signals at a different frequency, it
is in this case frequently not possible to preclude or avoid
multiple use of transmitted signals both at the same frequency and
with the same bit pattern within one project or one system, as a
result of which increased disturbance loads can occur.
[0006] The present invention is based on the object of specifying a
particularly simple apparatus of the type mentioned initially which
is particularly insensitive to disturbance influences at the same
time.
[0007] According to the invention, this object is achieved by an
apparatus for detection of the occupied or free state of a track
section having a transmitter for feeding a transmitted signal which
is coded by means of modulation, into the rails of the track
section and at least one receiver for receiving a received signal
which is produced by transmission of the transmitted signal via the
rails of the track section, wherein the apparatus is designed to
compare the modulation on the received signal with the modulation
on the transmitted signal.
[0008] Therefore, the invention is distinguished in that a solution
which is completely detached from the known concept is provided, in
that a receiver receives a received signal which is coded by means
of modulation and checks the modulation on the received signal by
comparison with modulation which is known at the receiver end and
is predetermined to be fixed for the relevant apparatus. Instead of
this, the corresponding check is carried out according to the
invention in that the apparatus is designed to compare the
modulation on the received signal with the modulation on the
transmitted signal. The association between the two signals is
therefore verified in a particularly simple manner by comparison of
the modulations on the received signal and on the transmitted
signal. This advantageously avoids the need to use rigid, fixed
predetermined codings, for example in the form of bit patterns, and
to permanently associate corresponding codings with the respective
apparatus. This advantageously also avoids corresponding effects
for configuration of the individual apparatuses, thus reducing the
production costs of the apparatus. Furthermore, the fitting process
is also simplified, thus additionally resulting in a time and
therefore cost saving. In addition, the configuration of a railroad
monitoring system is also simplified, since there is no need to
provide associations between codings or modulations and
apparatuses, and there is therefore also no need to store
corresponding associations on location plans and data sheets and to
subsequently take account of these. Furthermore, there are
advantageously also no restrictions relating to the number and the
nature of the modulations used for coding, thus creating the
precondition for making it possible to preclude multiple use of the
same modulations within one system.
[0009] It should be noted that, for the purposes of the apparatus
according to the invention, the transmitted signal is preferably an
audio-frequency signal. Furthermore, however, it is likewise
possible to use a transmitted signal at a frequency of below or
above the audio frequency range, or else in the form of a
direct-current signal.
[0010] The apparatus is preferably designed such that, when the
modulation on the received signal is compared with the modulation
on the transmitted signal, any discrepancy between the modulations
is found, and the track section associated with that apparatus is
immediately signaled as being occupied, in order to avoid
danger.
[0011] According to one particularly preferred embodiment, the
apparatus according to the invention is designed to produce a
transmitted signal (SIG.sub.S) which is coded by means of any
desired modulation, in particular random-number based. This is
advantageous because the use of any desired modulation, in
particular random-number based, as coding makes it possible to
virtually preclude any influence between two apparatuses in a
monitoring system resulting from the use of the same modulation. In
this case, any desired modulation may be used, because there is no
fixed association between the coding used and the respect apparatus
or the respective transmitter, and the way in which the coding is
produced ensures that it is possible to preclude with confidence
verging on certainty that two apparatuses would use the same
modulation within one system. Appropriate algorithms by means of
which random-number based coding of the respective transmitted
signal can be carried out, for example using random numbers or else
pseudo-random numbers are known per se from mathematics and
information technology, as a result of which these will not be
described in any more detail in the following text. It should be
noted that the use of any desired modulation, which is also in
particular random-number based or is generated on the basis of
random numbers, is made possible for the first time by the
apparatus according to the invention allowing comparison of the
modulation and therefore checking of the association between the
transmitted signal and the received signal without the receiver
needing to known in advance the modulation used for coding the
transmitted signal.
[0012] According to a further particularly preferred embodiment,
the apparatus according to the invention is designed to produce a
transmitted signal which is coded by means of frequency modulation.
This is advantageous because known apparatuses for detection of the
occupied or free state of a track section, for example in the form
of track circuits, frequently already use transmitted signals which
are coded by means of frequency modulation. This is because
frequency modulation is particularly insensitive to disturbance
influences during transmission. However, in addition to the use of
frequency modulation, it is in principle also possible to code the
transmitted signal by means of amplitude modulation or phase
modulation.
[0013] The apparatus according to the invention is preferably also
distinguished in that it is designed to produce a transmitted
signal which is coded by means of modulation in the form of a bit
sequence. For the purposes of this preferred development of the
apparatus according to the invention, the transmitted signal is
therefore coded by means of digital modulation in the form of a bit
sequence. This is advantageous because appropriate digital
modulation is particularly robust and insensitive to disturbance
influences. In this case, the bit sequence can preferably have any
desired length, that is to say, in particular, it is also possible
for the bit sequence to have an infinite length, as a result of
which it is generated continuously and is random because of the way
in which it is generated, as a result of which there is no fixed
bit pattern in the form that a part of the bit sequence is
regularly repeated.
[0014] In principle, the modulation on the received signal can be
compared in any desired manner with the modulation on the
transmitted signal. If the apparatus is designed to produce a
transmitted signal which is coded by means of modulation in the
form of a bit sequence, the apparatus according to the invention
can advantageously be designed such that it is designed for
bit-by-bit comparison of the modulation on the received signal with
the modulation on the transmitted signal. Particularly in the
comparison for use of codings with fixed, rigid bit patterns, a
bit-by-bit comparison of the modulation on the received signal with
the modulation on the transmitted signal is advantageous, because a
comparison such as this can be carried out very quickly.
Furthermore, and in contrast to the known procedure, the recovery
time after a disturbance event in which a transmitted bit is
destroyed is short, because there is no need for synchronization
and evaluation of bit patterns of predetermined length. Finally,
therefore, the availability of the apparatus is improved because of
the continuous information evaluation by the bit-by-bit
comparison.
[0015] According to a further particularly preferred development,
the apparatus according to the invention is designed for continuous
coding of the transmitted signal. This means that the transmitted
signal is coded continuously and permanently. This is advantageous
because the correct association between the transmitter and the
receiver, that is to say the reception of the received signal
resulting from the transmitter in the apparatus, can be verified
and therefore ensured at any time on the basis of the comparison of
the modulation on the received signal with the modulation on the
transmitted signal. As an alternative to continuous coding or
modulation of the transmitted signal, it is, however, also
feasible, depending on the respective circumstances and conditions,
for the transmitted signal to be coded only at times. On the one
hand, by way of example, this could be done by the transmitted
signal being coded with the modulation only at regular recurring
times, that is to say for example every 10 seconds. Furthermore, in
principle, an appropriate modulation could also be carried out only
in the course of a preferably regular functional test of the
apparatus.
[0016] According to one particularly preferred development of the
apparatus according to the invention, the apparatus is designed to
compare, in a manner which is safe from the signaling point of
view, the modulation on the received signal with the modulation on
the transmitted signal. This is advantageous because this reliably
precludes and avoids corruptions or errors in the course of the
comparison of the modulations. This is therefore of major
importance, in particular for all safety-critical apparatuses for
detection of the occupied or free state of a track section.
[0017] As already mentioned above, if, during the comparison of the
modulation on the received signal with the modulation on the
transmitted signal, the evaluation device finds a discrepancy
between the modulations, the apparatus indicates an occupied state
for the relevant track section. Furthermore, the apparatus
according to the invention can advantageously be distinguished in
that it is designed to produce a fault signal, which indicates a
disturbance state, based on the comparison of the modulation on the
received signal with the modulation on the transmitted signal. The
fault signal makes it possible to identify the existing disturbance
immediately and quickly and to overcome this as quickly as
possible, on this basis.
[0018] In principle, the fault signal which is produced may be
output in any desired manner. According to a further particularly
preferred embodiment, the apparatus according to the invention is
designed to output the fault signal in the form of a visual and/or
audible warning signal. This is advantageous because this makes it
possible to alert an operator, for example in a signal box, of the
existing disturbance particularly quickly and reliably.
[0019] The apparatus according to the invention can also
furthermore be designed such that the apparatus is designed to
transmit data signals via the rails of the track section to a rail
vehicle which is occupying the track section. This is advantageous
because the apparatus according to the invention can therefore
additionally be used in a manner known per se to transmit data
signals to a rail vehicle. This means that the apparatus according
to the invention can additionally be used for track-free signaling,
and, for example, for line train control.
[0020] Furthermore, the present invention relates to a method for
operation of an apparatus for detection of the occupied or free
state of a track section, wherein a transmitted signal, which is
coded by means of modulation, is fed into the rails of the track
section, and a received signal which results from transmission of
the transmitted signal via the rails of the track section is
received.
[0021] With regard to the method, the present invention is based on
the object of specifying a particularly simple method, which is at
the same time particularly insensitive to disturbances, of the type
mentioned above.
[0022] According to the invention, this object is achieved by a
method for the operation of an apparatus for detection of the
occupied or free state of a track section, wherein a transmitted
signal, which is coded by means of modulation, is fed into the
rails of the track section, and a received signal which results
from the transmission of the transmitted signal via the rails of
the track section is received, and the modulation on the received
signal is compared with the modulation on the transmitted
signal.
[0023] The advantages of the method according to the invention
correspond to those of the apparatus according to the invention, as
a result of which reference is made in this context to the
corresponding statements above. This also applies to the preferred
developments of the method according to the invention mentioned in
the following text, in respect of the corresponding preferred
developments of a apparatus according to the invention, as a result
of which reference is likewise made in this context to the
corresponding statements above.
[0024] The method according to the invention can preferably be
carried out such that the transmitted signal is coded by means of
any desired modulation, in particular random-number based.
[0025] According to a further particularly preferred embodiment of
the method according to the invention, the transmitted signal is
coded by means of frequency modulation.
[0026] Advantageously, the method according to the invention can
also be distinguished in that the transmitted signal is coded by
means of modulation in the form of a bit sequence.
[0027] The method according to the invention can preferably also be
carried out in that the modulation on the received signal is
compared bit-by-bit with the modulation on the transmitted
signal.
[0028] According to a further particularly preferred development of
the method according to the invention, the transmitted signal is
coded continuously.
[0029] According to one particularly preferred embodiment, the
method according to the invention is carried out such that the
modulation on the received signal is compared, in a manner which is
safe from the signaling point of view, with the modulation on the
transmitted signal.
[0030] According to a further particularly preferred embodiment of
the method according to the invention, a fault signal which
indicates a disturbance state is produced on the basis of the
comparison of the modulation on the received signal with the
modulation on the transmitted signal.
[0031] According to a further particularly preferred refinement of
the method according to the invention, the fault signal is output
in the form of a visual and/or audible warning signal.
[0032] Preferably, the method according to the invention can also
be developed such that data signals are transmitted via the rails
of the track section to a rail vehicle which is occupying the track
section.
[0033] The invention will be explained in more detail in the
following text with reference to one exemplary embodiment. For this
purpose, and in order to explain one exemplary embodiment of the
method according to the invention,
[0034] The FIGURE shows a schematic sketch of an arrangement having
one track section, as well as one exemplary embodiment of the
apparatus according to the invention.
[0035] The FIGURE illustrates an apparatus V for detection of the
occupied or free state of a track section G. The apparatus V has a
transmitter S for feeding a transmitted signal SIG.sub.S in the
form of an AC voltage into the rails F of the track section G.
Furthermore the apparatus V has a receiver E for receiving a
received signal SIG.sub.E which is produced by transmission of the
transmitted signal via the rails F of the track section G.
[0036] As shown in the illustration in the FIGURE, an AC voltage at
the frequency f1 is fed into the track section G. In order to make
it possible to reliably distinguish between the respective signals,
the adjacent track sections are operated with an AC voltage at a
different frequency f5 or f3. The following text assumes that the
arrangement illustrated in the FIGURE is an audio-frequency track
circuit having a plurality of frequencies, in which an AC voltage
in the form of a transmitted signal SIG.sub.S in the
audio-frequency range is fed into rails F of the track section
G.
[0037] By way of example, the apparatus V may be arranged in a
signal box of a railway system, or a railway monitoring system.
This offers the advantage that particularly high reliability is
achieved since mechanical loading and climatic influences have less
influence on the electronic components in the apparatus V than
would be the case if these components were accommodated in the
vicinity of the track. Furthermore, this results in further
advantages with respect to availability and maintenance of the
apparatus V, that is to say in particular of the transmitter S and
of the receiver E. The horizontal dashed-dotted line in the FIGURE
indicates corresponding separation between the internal system,
which is associated with the apparatus V, and the external system,
which is associated with the track section G.
[0038] As shown in the illustration in the FIGURE, track connecting
housings GAG1, GAG2 are arranged on the trackside and are used to
introduce the transmitted signal SIG.sub.S, which is fed in and
provided by the transmitter S, and to read out the received signal
SIG.sub.E, which is transmitted to the receiver E, respectively
into and out of the rails F. In this case, the track connecting
housings GAG1, GAG2 normally do not contain any active electronic
components, but essentially only a resonant circuit for
frequency-selective amplification of the signals fed in and fed out
at a predetermined useful frequency, that is to say the frequency
f1 of the transmitted signal SIG.sub.S and of the received signal
SIG.sub.E in the case of the track section G illustrated in the
FIGURE.
[0039] The transmitted signal SIG.sub.S from the transmitter S is
coded by means of modulation. Appropriate codings are used in order
to improve the reliability in the event of disturbance influences,
that is to say for example to reduce the probability of an
appropriated coded transmitted signal SIG.sub.S being simulated by
disturbance amplitudes. In this case, corresponding disturbances
can be caused on the one hand by external sources, but on the other
hand also by other apparatuses V, that is to say for example by
track circuits arranged in the vicinity.
[0040] In the case of track circuits known from the prior art, a
fixed predetermined, rigid coding is normally modulated on at the
transmitter end, is transmitted, and the coding is read out at the
receiver end and compared with the fixed predetermined coding
associated with the respective track circuit. Because of the use of
rigid bit patterns, multiple use of the same bit pattern cannot be
completely precluded, even when the same signal frequency is used.
This increases the disturbance load on the track circuits.
Furthermore, the recovery time after a disturbance event with bit
destruction is comparatively long because of the synchronization
required with regard to the fixed bit pattern and the evaluation of
bit sequences of predetermined length required for this purpose. In
practice, this leads to a further restriction to the availability
of the apparatus.
[0041] In the exemplary embodiment as shown in the FIGURE, the
disadvantages mentioned above are avoided in that the apparatus V
is designed to compare the modulation on the received signal
SIG.sub.E with the modulation on the transmitted signal SIG.sub.S.
This makes it possible to verify that the received signal SIG.sub.E
received by the receiver E has also actually been produced by the
transmitted signal SIG.sub.S fed by the transmitter S.
[0042] The comparison of the received signal SIG.sub.E with the
transmitted signal SIG.sub.S advantageously makes it possible to
produce a transmitted signal SIG.sub.S which is coded by means of
any desired modulation, in particular random-number based, and to
feed this into the rails F of the track section G. The transmitted
signal SIG.sub.S is preferably a transmitted signal coded by means
of frequency modulation, with the apparatus V preferably generating
a continuous "bit sequence stream", randomly. This bit sequence
stream is modulated onto the transmitted signal SIG.sub.S and,
after being transmitted via the rails F of the track section G, is
read out at the receiver end by means of the received signal
SIG.sub.E.
[0043] According to the exemplary embodiment in the FIGURE, the
apparatus V also has an evaluation device AE, in addition to the
transmitter S and the receiver E. The evaluation device AE is used
on the one hand to produce the bit sequence stream, that is to say
the coding in the form of the continuous bit sequence. The
evaluation device AE transmits the bit sequence that is produced to
the transmitter S, which transmits the transmitted signal
SIG.sub.S, which is coded by means of the modulation in the form of
the bit sequence, in order to be fed into the rails F of the track
section G. On the other hand, the evaluation device AE also
receives from the receiver E the received signal SIG.sub.E and the
coding, determined from the received signal SIG.sub.E, in the form
of the corresponding frequency modulation. This makes it possible
for the evaluation device AE to carry out a bit-by-bit comparison
of the modulation on the received signal SIG.sub.E, with the
modulation on the transmitted signal SIG.sub.S. In this case,
bit-by-bit comparison offers the advantage that this can be carried
out quickly. The evaluation device AE is preferably designed to
compare, in a manner which is safe from the signaling point of
view, the modulation on the received signal SIG.sub.E with the
modulation on the transmitted signal SIG.sub.S. The signaling
certainty of the evaluation device AE can in this case be ensured
by architecture measures which are known in their own right and are
required in order to achieve the safety level normally required in
the field of railroad technology. By way of example, corresponding
measures may comprise the evaluation device making use of two
channels throughout and the use of safe computers.
[0044] In accordance with the above statements, there is
advantageously no need for rigid bit patterns, defined in advance,
for the purposes of the apparatus according to the invention and
the method according to the invention. Particularly as a result of
the transmitted signal being coded by means of any desired
modulation, in particular a random-number based, this makes it
possible to virtually preclude any influence between two
apparatuses, that is to say for example track circuits, resulting
from the same codings or bit information.
[0045] Overall, therefore, the present invention results in
considerable advantages with respect to reducing the disturbance
arising within a project or a system. Furthermore, the continuous
information evaluation, that is to say the bit-by-bit comparison,
improves the availability of the apparatus V, without any need for
complex synchronizations depending on the length of a rigid bit
pattern that is used, for example in the event of bit
destruction.
[0046] Furthermore, there is advantageously no need to set a bit
pattern which is in each case permanently associated with the
respective track section G and the respective apparatus V of the
track section G by appropriate setting-up or configuration, for
example by using so-called bit pattern plugs, at the transmitter
end and receiver end. This reduces the number of components
required for the apparatus V, and saves time for assembly of the
apparatus V. Furthermore, the setting-up process is also simplified
because there is no need to associate bit patterns with track
circuits in location plans and data sheets. Furthermore, the use of
the method according to the invention and the apparatus according
to the invention makes it possible to virtually completely dispense
with restrictions relating to a line and cable routing, since
thorough reliable checking is possible to determine whether a
received signal SIG.sub.E received by the receiver E actually
relates to the relevant track section G. The only exception in this
case is that the lines of the transmitter S and of the associated
receiver E for the same track section G and the same apparatus V
should still be routed separately from one another, in order to
prevent coupling or crosstalk of the transmitted signal SIG.sub.S
into the line of the receiver E. Corresponding to the above
statements, one important reason that the restrictions relating to
cable routing can be dispensed with is that identical bit sequences
for different apparatuses V can be virtually precluded, in
particular even in the case in which the bit sequence for coding of
the transmitted signal SIG.sub.S is generated on a random-number
basis.
[0047] In summary, it can therefore be stated that the embodiment
of the apparatus V according to the invention as shown in the
FIGURE allows an increase in the disturbance insensitivity of the
apparatus V for detection of the occupied or free state of the
track section G and at the same time achieving a simplification
and, associated with this, a cost reduction.
* * * * *