FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A digital axle-counter system for making railway signalling controls highly available
APPLICANT
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030,
Maharashtra, India, an Indian Company
INVENTORS
Namjoshi Yogendra of Crompton Greaves Ltd , Electronic Development Centre, Global R&D,
Crompton Greaves, limited, Kanjurmarg, Mumbai-400042, Maharashtra, India, Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to
be performed:

FIELD OF THE INVENTION.
The present invention relates to digital axle-counter systems and more
particularly, to digital axle-counter system used in railway signalling.
DESCRIPTION OF THE BACKGROUND ART
With the advancement in semiconductor technology, various railway
signalling and traffic control systems are adopting programmable digital electronics towards making systems compact, scalable and maintainable. One of the common electronic devices in railway signalling is a Digital Axle Counter System (DACS) used in guide rails. As compared its traditional counterpart - the track circuits the DACS delivers additional features, apart from the basic requirement of track occupancy, viz. wheel counts, direction, speed, length of the train etc. The conventional digital axle counter design typically consists of two transmitters and two receivers sensing design, or otherwise called as double wheel detectors. Under failure of any one of these sensing units or its related electronics the system runs into its safe state that is track-occupancy and the error condition is sent to the control unit. This runs the unavailable or non-operative. As a result, such unavailability requires immediate personnel attention and manual supervision and therefore is a major limitation in railway signalling. In metro and suburban transit rail scenario at peak time, such a failure in the conventional system creates lot of inconvenience for commuters.
Attempts have been made to solve the above problem by way of adding
redundancy in the DACS. However, redundancy alone cannot ensure reliability or safety of a system in operation. Many railway signaling and traffic control systems use redundancy at the system level rather that at individual board level. Software redundancy is also a key method to generate fault tolerant systems. In such a scenario, the software has to detect the error in real-

time and formulate an alternative methodology to maintain the system in operational mode or secondary operational mode through the available redundant hardware. However, promoting redundancy in hardware and design is not a cost-effective solution instead majority of the task should be undertaken in the software itself, rather than building redundancy at system level which is absent in current DACS.
An illustrative example of a recent DACS includes, a pair of electromagnetic
inductive sensor-set, each of which further comprises of a transmitter and a receiver, a signal conditioning circuit and a logic circuit. The two sets are separated by a distance such that when the wheel passes through them both the receivers are affected in a small period of time. When a train wheel passes the DACS sensor sets, the flange cuts the electromagnetic flux and is sensed by the receivers. The sensor output signals are processed and fed to the two microcontrollers which simultaneously sense the activity on the sensors and immediately cross-tally or double-check with each other after one event. If the right sensor is triggered first, the direction is considered east-ward, or say, in-ward. Similarly if the left sensor is triggered before the right sensor, the direction is considered west-ward, or say, out-ward. Any sequence of transition will declare the track occupied.
Two such DACS units are placed at extreme ends of the track section it
administers. Each DACS stores the number of wheels and communicates to the other end DACS. Once other end DACS senses equal number of wheels in the exit direction, the track is declared to be clear. However, if any of the sensors fails, the direction cannot be determined and hence the system becomes unavailable.
Thus, there is a need to provide a DACS that overcomes at least some of the
above noted drawbacks.

SUMMARY OF THE INVENTION
An object of the invention is to provide a digital axle counter unit with high
availability, which axle counter continues working in case of any single sensor related fault.
Another object of the invention is to provide a digital axle counter with ease in
maintenance, achieved through indication of the exact fault location in the axle counter unit while without going into unavailable mode.
Accordingly disclosed herein is a digital axle-counter system for making
railway signalling controls highly available for rail-bound vehicles that includes at least three electrically isolated sensor sets disposed along a section of a guide rails in spaced apart relationship with each other and in a direction parallel to the guide rails, each of the three sensor sets being sequentially activated on each wheel count of a rail-bound vehicle, a first microcontroller and a second microcontroller electrically connected with each other, the first microcontroller electrically connected with a first sensor set, the second microcontroller electrically connected with a third sensor set, and a second sensor set electrically connected to both the first and the second microcontrollers, each of the sensor sets sequentially sending signals in isolation to the corresponding first and the second microcontrollers when activated. and an identical intelligent software adapted for running on both the first and the second microcontrollers embedded therein, the intelligent software defining a timed state machine having a plurality of sequentially achievable states corresponding to the sequential signals received from the corresponding sensor sets, the timed state machines traversing from a current state to a new state based on each of the received signals, wherein, the timed state machines of the corresponding microcontrollers are programmed to interrogate each other on attaining predetermined new states so as to determine occupancy of the section of the guide rails and also

if any one of the sensor sets or the microcontrollers have failed and wherein, the timed state machines are programmed to interrogate each other on completion of the sequential steps and based on the sequential steps followed by at least one of the timed state machines, determining direction of travel of the rail-bound vehicle.
According to various embodiments of the present invention, the plurality of
sequentially achievable states of the timed state machine of the first microcontroller includes a first plurality of achievable states for determining occupancy and direction of the rail-bound vehicle in the east direction, and a second plurality of achievable states for determining occupancy and direction of the rail-bound vehicle in the west direction.
According to various embodiments of the present invention, the timed state
machine of the first microcontroller traverses to a second state and the timed state machine of the second microcontroller traverses to a fifth state when the second sensor set is activated, and wherein both the first and the second microcontrollers interrogate each other to determine whether both the microcontrollers have received signals from the second sensor set, and further wherein the above step is repeated when the timed state machine of the first and the second microcontrollers traverses to fourth and seventh state, respectively.
According to various embodiments of the present invention, if it is determined
by any one of the microcontrollers that the other one is not responding, by returning a 'null' state or 'no' state signal then a signal is sent to a reset box electrically connected with the microcontrollers to replace the identified faulty sensor set.
According to some embodiments, when the rail-bound train is travelling in the
west direction and the first sensor set fails, the first microcontroller remains at the 'Null' state whereas the timed state machine of the second microcontroller traverses to the new states by

getting signal from the second and the third sensor sets, and wherein signals received from the second and the third sensor sets determine occupancy of the section of the guide rails and direction of travel of the rail-bound vehicle.
According to some embodiments, when the rail-bound train is travelling in the
east direction and the third sensor set fails, the second microcontroller remains at the 'Null' state whereas the timed state machine of the first microcontroller traverses to the new states by getting signal from the first and the second sensor sets, and wherein signals received from the first and the second sensor sets determine occupancy of the section of the guide rails and direction of travel of the rail-bound vehicle.
According to some embodiments, when the rail-bound train is travelling in
either east or west direction and the second sensor set fails, the intelligent software embedded in both microcontrollers symbiotically performs special transits to new states by getting signal from the first and the third sensor sets, and wherein signals received from the first and the third sensor sets determine the occupancy of the section of the guide rails and direction of travel of the rail-bound vehicle.
It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.

A BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of the various
embodiments of the invention, and the manner of attaining them, will become more apparent and will be better understood by reference to the accompanying drawings, wherein:
FIG. 1 illustrates a schematic view of at least three sensor sets configuration
disposed adjacent to guide rails for detecting wheels of a rail-bound vehicle according to an embodiment of the present invention;
FIG. 2 shows a schematic diagram of isolated processing units and their
connections to the at least three sensor units of FIG. 1 according to an embodiment of the present invention:
FIG. 3 shows a timed state machine layout present within both the processors
of FIG. 2 according to an embodiment of the present invention;
FIG. 4 is a representation of timed state machines of both the processors and
their intercommunication through predetermined updates for a rail-bound vehicle in East-ward direction;
FIG. 5 is a representation of timed state machines of both the processors and
their intercommunication through predetermined updates for a rail-bound vehicle in East-ward direction;
FIG. 6 shows intercommunication between both the processors in the case
when a third sensor set C fails; and
FIG. 7 shows intercommunication between both the processors in the case
when the second sensor set B fails.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates schematic view of track side equipment of a general Digital
Axle Counter System (DACS) 100 configured with guide rails 102 on which any of rail-bound vehicle (not shown) moves, according to an embodiment of the present invention. It is to be noted that for the purposes of the specification, the DACS 100 is used in railway signalling control. However various other applications of the present invention where signalling and control of traffic of other vehicles is concerned may also considered being within the scope of the present invention. The DACS 100 includes at least three pairs of sensor sets (set A, set B. and set C) disposed along a 'section' of a guide rails 102 and positioned in spaced apart relationship with each other. Further, each of the sensor sets is also disposed in a direction parallel to the guide rails 102. Preferably, each of the sensor set comprises of a transmitter 104 and a receiver 106, a signal conditioning circuit 108 and a logic circuit 110. The distance between each of the three sets is set in such a manner that when the wheel of a rail-bound vehicle passes them all of the receivers 106 are commonly affected in a small period of time. Similarly, plurality of the sensor sets are positioned on a desired length of the guide rails 102 for controlling traffic of railway signals depending on the need. It is to be understood that similar DACS 100 systems are positioned alongside the guide rails 102 at regular intervals and are configured with each other to intercommunicate to share and update the occupancy of the gijide rails 102 and determination of direction of travel of the rail-bound vehicle. In this manner, an effective control of the railway traffic may be established between the sections of the guide rails 102.
As shown in FIGS. 1 & 2, the sensor sets are electrically connected to a first
processor and a second processor hereinafter referred as a first microcontroller 112 and a second microcontroller 114 in known manner. Preferably, the first and the second microcontrollers 112, 114 are electrically isolated with each other but are interoperable 116 as described in the

following description. Further, the first microcontroller 112 is electrically connected with a sensor set (set A), the second microcontroller 114 is electrically connected with a sensor set (Set C), and a sensor set (set B) is electrically connected to both the first and the second microcontrollers 112,114 . or common, as shown in FIGS. 1&2. Thus, sensor sets A & B forms processor Section 1 and the sensor sets B & C forms processor Section II.
The sensor output signals from each of the sensor sets (set A, set B, and set C)
are sequentially processed in to the corresponding first and the second microcontrollers 112,114 when activated. Further, each of the sensor sets (set A, set B, and set C) and its corresponding circuitry is electrically isolated from each other so that signals processed from one of the sensor sets doss not influences the other sensor set and in the unforeseen scenario of one of the sensor set being subjected to failure, the other sensor sets keep on Operating. When a wheel of a rail-bound vehicle travels on the guide rails 102 and passes through the three sensor sets(set A, set B, and set C). the signals from the transmitters 104 are communicated through transformers (not shown) and opto-isolators to their corresponding receivers 106. Based on these, the receiver signal conditioning circuit 108 a digital output that is communicated through opto-isolation to the corresponding microcontrollers. Thus, if the condition of each of the sensor set (set A, set B, and set C) is good, sequentially all of the sensor set (set A, set B; and set C) will be activated on each wheel count of a rail-bound vehicle.
Typically, in known systems such as conventional 2-out of-2 architecture, the
processors/microcontrollers confirm the in-wheel or out-wheel at the end of the complete event i.e. at the end of complete sequence. Further, many conventional systems also use timer based sensing. A well known, such sensing systems can be improved with interrupt based system that is asynchronous to processor clock and any intermediate event can be- sensed in real-time.

Further, with the advancement in recent programmable devices FPGAs, microcontroller and DSPs, high computation speeds can be achieved. This enables improvement in sensing the edges as well as communicating at higher speeds for confirmation. The proposed software architecture (as described in the following description) uses both of these advantages to communicate on intermediate trigger pulses, thanks to high speed microcontroller cores. Similarly, FPGAs can be used as their designs are inherently parallel and serves equally efficient in sensing and communication at par with advanced microcontrollers. A skilled person would be able to understand the benefits of interrupt based system based on the above technologies in the following detailed description.
Both the first microcontroller 112 and the second microcontroller 114 run on
an identical intelligent software that defines a distributed times finite state machine 118. Further, each of the timed state machines 118 has a plurality of sequentially achievable states 120 corresponding to the sequential signals received from the corresponding sensor sets and each of the timed state machines 118 traverses from a current state 120 to a new state 120 based on each of the received signals. Further, the distributed timed finite state machine 118 requires communication between the first and the second microcontrollers/processing units 112,114 and synchronization in timing. This is taken care through a high speed serial communication between the processors with compact protocols, preferably in one or two bytes, to convey the status. A synchronization clock (not shown) can be delivered by either of the processor helps timed finite state count to be in-sync with each other. In other words, the processor unit that sources the clock can be called as Master Processor Unit (Microcontroller/Processor ]) and the neighboring processor is called Slave Processor Unit (Microcontroller/Processor 2). Failure of the clock simply means the sourcing section has failed and the system runs into secondary mode, as

described later, without compromising on the availability of the section of the guide raits 102. All the timed states in the FSMs are responsible to perform error sensing and if not fatal, continuing operation in the secondary mode.
Reference will now be given to FIG. 3 that illustrates timed state machine 118
running in both the microcontrollers/processors. In the FIG. 3. X and Y represent processed wheel detector outputs/signals from the signal conditioning circuitry 108 of sensor sets (set A, set B, and set C) to the corresponding microcontrollers/processors. The transitions are driven by positive edge and negative edge triggers the inputs. For example, +X indicates that wheel flange has cut the sensor X whereas -X represents that the wheel flange has passed out of the sensor X. Thus, a conventional stateless automata system would expect +X, +Y, -X and -Y in an eastward direction. Apart from default timeless states, four timed states 120 are introduced. These timed states 120 require inputs (or interrogation) from the neighbouring processor's state-machine in a stipulated time against confirming its own inputs. This interrogation is done so as to determine occupancy of the section of the guide rails 102 and also if any one of the sensor sets (set A. set B, and set C) or the microcontrollers have failed. Further, interrogation between each other is also done on completion of the sequential steps and based on the sequential steps followed by at least one of the timed state machines 118 in any one of the microcontrollers/processors, direction of travel of the rail-bound vehicle is also determined. This is also the pivotal point of detection of errors in real time which instantiates immediate shifting to secondary mode. In FIG. 3, for understanding of a skilled person, the circles with slice represent timed states 120. Such states input from local processor's previous state 120 and neighbouring processor's state 120 marked with dashed number.

Referring now to FIG. 4 that illustrates detailed intercommunication between
the distributed state machines 118 of both the microcontrollers/processors through predetermined updates/interrogation on attaining predetermined new states 120 in both the timed state machines 118. This is done so as to determine occupancy of the section of the guide rails 102 and also if any one of the sensor sets (set A, set B. and set C) or the microcontrollers have failed. Further. the interrogation done on completion of the sequential steps of each of the timed state machine 118, and based on the sequential steps followed by at least one of the timed state machines 118. determines direction of travel of the rail-bound vehicle. These are the objectives that will be understood on careful analysis of the detailed intercommunication between the distributed state machines 118 of both the microcontrollers/processors, as described below.
The plurality of sequentially achievable states 120 of the timed state machine
118 of the first microcontroller 112 includes a first plurality of achievable states (states 0-1-2-3-4-Confirmation-O) for determining occupancy and direction of the rail-bound vehicle in the east direction, and a second plurality of achievable states (states 0-7-6-5- Confirmation-0) for determining occupancy and direction of the rail-bound vehicle in the west direction. Further, the timed state machine ) 18 of the second microcontroller 114 act as a mirror image of the timed state machines 118 of the first microcontroller 112 with the first plurality of achievable states (states 0-5-6-7-Confirmation-0) determining occupancy and direction of the rail-bound vehicle in the east direction, and the second plurality of achievable states (states 0-l-2-3-4-Confirmation-0) determine occupancy and direction of the rail-bound vehicle in the west direction. Between the first plurality of sequentially achievable states 120 and the second plurality of sequentially achievable states 120 there is a 'null' state and the plurality of sequentially achievable states 120 are repeated depending on the direction of travel of the rail-bound vehicle. For the purpose of

explaining the working principle of the invention, reference will be given to the rail-bound train travelling in the East direction. However, it will be clearly understood to a skilled person that the working principle is also applicable to the rail bound vehicle in the west direction.
Reference will now be given to FIG. 4. that illustrates the primary or the
normal mode in which it is assumed that all the sensor sets (set A, set B, and set C) are working in good condition and fully operable to sense the direction of the rail-bound vehicle as well as the occupancy of the vehicle on a section of a railways track, When the sensor set A senses the wheel, the sensor set A sends signal to the microcontroller/processor 1. This is shown by transition on +A which belongs only to processor 1 and accordingly the state machines 118 reverse to state 1.When the wheel is sensed by the senser set B, the sensor set B sends signals to the timed state machines 118 of the microcontroller/processor 2. This is shown by transition to +B the processor 2 and accordingly the state machines 118 traverses to state 5. Thereafter, the microcontroller/processor 2 sends interrogates/update microcontroller/processor 1. Thus, both the first and the second microcontrollers 112,114 interrogate/update each other to determine whether both the microcontrollers have received signals from the sensor set B. Upon +B, before traversing to state 2 microcontroller/processor 1 waits for update from state 5' i.e. the neighbouring microcontroller/processor. When the update arrives in time, the timed state machines 118 of the microcontroller/processor 1 traverses to state 2. as shown in FIG. 4. Waiting for further wheel detection transition on -A, state machines 118 in microcontroller/processor 1 traverses to state 3. Likewise to state 2, upon transition on -B the microcontroller/processorl based on inputs from 7 i.e. from neighbouring microcontroller/processor traverses to state 4 and sends C1 otherwise E update to microcontroller/processor 2, and also waits for same from microcontroller/processor 2. After such an update arrives, the microcontroller/processorl

increments the E-counter and goes back to initial state, waiting for further wheel detection. A plurality of above sequence but in opposite manner occurs in reverse direction i.e. the westward as shown in FIG. 5.
Reference will now be given to FIG. 6. that illustrates the failure condition of
any 'one' of the extreme sensor sets A, or C during operation. This is known as the secondary mode in which the DACS 100 operates. It will be assumed that in the first place, sensor set C Objective of discussing the failure of the sensor sets is that even though any one of the sensor set fails, the section of the track is available for the rail-bound vehicles to occupy and also the direction of the rail-bound vehicle is sensed. Thus, the DACS 100 system allows the railway signalling controls to be highly available.
In the first case when sensor set C fails, assuming that sensor set C fails before
arrival of the rail-bound vehicle i.e. when the track was clear. Under such circumstance, microcontroller/processor 1 continues to work and senses that there are no communication inputs from its neighbouring microcontroller/processor 2. The microcontroller/processor 2 continues until the rail-bound vehicle is sensed and declares track occupied. Accordingly, direction of the rail-bound vehicle is also determined as the sensor set B will be activated prior to the sensor set C. Similar case applies to failure of sensor set A and processor 2. Based on these conditions the cause for the failure will be determined and communicated to the control unit. The track-side unit will continue to function until the system is rectified and a reset is forced from the control unit. Generally, the reset is present with the station master.
In the case where sensor set B fails, the explanation will be provided with the
help of FIG. 7. As shown in FIG. 3 the intelligent software based on timed state machines have some special transitions viz. firstly, intra-state machine transition from state 1 to state 7 and

skipping the transitions of Y and secondly, inter-state interrogation communication for detecting both microcontroller traverse to state 1 one after another. These special transitions are meant for continuing operation in case of sensor set B failure. Consider a rail-bound vehicle travelling East ward. As shown in FIG. 7. microcontroller/processor 1 will get a signal from sensor set A and it will traverse to state 1. As a special update it will send an interrogation to microcontroller/processor 2 which is in state 0 which remembers it. If microcontroller/processor 2 due to failure of sensor set B, receives its first signal from signal set C, it will use previous interrogation of microcontroller/processor 1 which is also in state 1 and so it traverses to state 7. during which it will also send an interrogation to microcontroller/processor 1. This being a special case, failure in sensor set B will be detected by microcontroller/processor I and will update its state machine to traverse to state 2 and skips all transition signals required from sensor set B. Upon entering the state 7 it will send an interrogation update to microcontroller/processor 1 for future. After receiving signal from sensor set A, that is -A, the microcontroller/processor 1 will skip all sensor set B transitions and will wait for confirmation from microcontroller/processor 2. Upon receiving signal from sensor set C, that is -C, the microcontroller/processor 2 traverses from state 7 to confirmation state where it will update microcontroller/processor 1. It should be noted that timeliness of the states under failure is redundant and will be ignored in special cases. Upon confirmation, both microcontrollers/processors will update their E-counter and revert back to initial states. The error messages with specification will be sent to the reset box. Similar plurality holds true for rail-bound vehicle travelling in West ward direction and two state machines will perform in reverse manner to the way described above.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

We Claim:
1. A digital axle-counter system for making railway signalling controls highly available for rail-bound vehicles, the system comprising:
at least three electrically isolated sensor sets, each of them comprising of a pair of transmitter and receiver sensor coils electrically coupled with electronic circuitry for driving and processing the received signals respectively, disposed along a section of a guide rails in spaced apart relationship with each other and in a direction parallel to the guide rails, each of the three sensor sets being sequentially activated on each wheel count of a rail-bound vehicle;
a first microcontroller and a second microcontroller electrically connected with each other, the first microcontroller electrically connected with a first sensor set, the second microcontroller electrically connected with a third sensor set, and a second sensor set electrically connected to both the first and the second microcontrollers, each of the sensor sets sequentially sending signals in isolation to the corresponding first and the second microcontrollers when activated; and
an identical intelligent software adapted for running on both the first and the second microcontrollers embedded therein, the intelligent software defining a timed state machine having a plurality of sequentially achievable states corresponding to the sequential signals received from the corresponding sensor sets, the timed state machines traversing from a current state to a new state based on each of the received signals,
wherein, the timed state machines of the corresponding microcontrollers are programmed to interrogate each other on attaining predetermined new states so as to determine occupancy of the section of the guide rails and also if any one of the sensor sets or the microcontrollers have failed and wherein, the timed state machines are programmed to interrogate each other on

completion of the sequential steps and based on the sequential steps followed by at least one of the timed state machines, determining direction of travel of the rail-bound vehicle.
2. The digital axle-counter system according to claim 1. wherein the plurality of sequentially achievable states of the timed state machine of the first microcontroller includes a first plurality of achievable states for determining occupancy and direction of the rail-bound vehicle in the east direction, and a second plurality of achievable states for determining occupancy and direction of the rail-bound vehicle in the west direction.
3. The digital axle-counter system according to claim 2, wherein the timed slate machine of the second microcontroller is a mirror image of the timed state machine of the first microcontroller with the first plurality of achievable states determine occupancy and direction of the rail-bound vehicle in the east direction, and the second plurality of achievable states determine occupancy and direction of the rail-bound vehicle in the west direction.
4. The digital axle-counter system according to claim 2 and 3, wherein between the first plurality of sequentially achievable states and the second plurality of sequentially achievable states there is a 'null' state and wherein within both of the microcontrollers, the plurality of sequentially achievable states are repeated depending on the direction of travel of the rail-bound vehicle.
5. The digital axle-counter system according to claim 2, wherein the timed state machine of the first microcontroller traverses to a second state and the timed state machine of the second microcontroller traverses to a fifth state when the second sensor set is activated, and wherein

both the first and the second microcontrollers interrogate each other to determine whether both the microcontrollers have received signals from the second sensor set, and further wherein the above step is repeated when the timed state machine of the first and the second microcontrollers traverses to fourth and seventh state, respectively.
6. The digital axle-counter system according to claim 4, wherein if it is determined by any one of the microcontrollers that the other one is not responding, by returning a 'null' state or 'no' state signal then a signal is sent to a reset box electrically connected with the microcontrollers to reset the settings or to replace the sensor sets after the section of the track is cleared.
7. The digital axle-counter system according to claim 1, wherein when the rail-bound train is travelling in the east direction and the first sensor set fails, the first microcontroller remains at the 'Null' state whereas the timed state machine of the second microcontroller traverses to the new states by getting signal from the second and the third sensor sets, and wherein signals received from the second and the third sensor sets determine occupancy of the section of the guide rails and direction of travel of the rail-bound vehicle.
8. The digital axle-counter system according to claim 1, wherein when the rail-bound train is travelling in the east direction and the third sensor set fails, the second microcontroller remains at the 'Null' state whereas the timed state machine of the first microcontroller traverses to the new states by getting signal from the first and the second sensor sets, and wherein signals received

from the first and the second sensor sets determine occupancy of the section of the guide rails and direction of travel of the rail-bound vehicle.