Patent Publication Number: US-2022234632-A1

Title: Broken rail detector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 17/070,693, entitled “Broken Rail Detector”, filed on Oct. 14, 2020, which itself claims priority to and the benefit of the filing of U.S. Provisional Patent Application No. 62/914,751, entitled “Broken Rail Detector”, filed on Oct. 14, 2019, and the specifications and claims (if any) are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Embodiments of the present invention relate to a method and apparatus to detect breaks in a track, such as a rail line, and the ability to detect the presence of a train or rail car or other rail vehicles with conductive axles in a monitored section of track. 
     Existing technologies for detecting breaks in railroad tracks usually require significant modifications to the rail or the addition of various types of sensors, which can include wires and/or fiber optics. Such known systems suffer from high installation costs, often require complicated maintenance procedures which necessitate specialized personnel and equipment. Such known systems can result in detection reliability errors caused by the severe conditions that most railroad tracks experience. Existing technology for detecting the presence of trains in a section of rail usually involve the wheels and axles completing a circuit in an isolated section of rail, proximity detection of the metal in the train, or detection of identification transponders mounted to locomotives and/or rail cars. Rail isolation can be achieved by using shunts of different types and in some cases insulated joints. Insulated joints associated with rail crossings are common in urban areas. 
     There is thus a present need for a method and apparatus that involves only minor cost, minor modifications to the installation of new or existing rails, no additional infrastructure installation, and no specialized installation and maintenance personnel. There is further a present need for a method and apparatus which has significantly lower susceptibility to environmental effects on a rail track than do existing technologies. 
     BRIEF SUMMARY OF EMBODIMENTS OF THE PRESENT INVENTION 
     Embodiments of the present invention relate to a detector that includes a circuit configured to inject at least two frequencies of alternating electrical current into a shunted segment of a track, and the circuit configured to measure an amplitude difference and a phase angle between the at least two frequencies of alternating current and identify a break in at least a portion of the track based on a change in the measured amplitude difference and phase angle. The track can include a rail track. The shunted segment of the track can include an electrical shunt disposed at opposing ends of the shunted segment of the track. Optionally, the electrical shunt can include an electrical conductor that is electrically connected between two rails of the shunted segment of the track. The circuit can be electrically connected at or about a midpoint of the shunted segment of the track. 
     In one embodiment, the circuit can be configured to monitor current flow to the shunted segment of the track, and/or configured to measure an amplitude of the at least two frequencies of alternating electrical current to cancel out common parasitic resistance of the shunted segment of the track. The detector can also include a communications unit. The communications unit can be configured to provide data telemetry. Optionally, the communications unit can include a radio frequency transmitter. The detector can be configured to transmit data and to relay data received from another detector. Optionally, the detector can also include a communication node configured to receive data from the detector and the communication node can be configured to transmit the data. In one embodiment, the circuit does not determine a break in the track merely by identifying a drop in current flow through all or a portion of the shunted track segment. 
     Embodiments of the present invention also relate to a method for detecting a break in at least a portion of a track, the method including forming a track segment by establishing an electrical shunt at each end of the track segment, injecting at least two frequencies of alternating electrical current into the track segment, monitoring a phase angle between the at least two frequencies of alternating current, and transmitting data indicative of a break in the track. Establishing an electrical shunt at each end of the track can include selecting a portion of track which is bounded by at least one existing electrical shunt. The track can include a rail track. 
     In one embodiment, indicia of a break is generated in response to an observed positive amplitude shift from a baseline reference point for a lower of the two frequencies of alternating current in addition to a negative phase shift being observed in a higher of the two frequencies of alternating current. In one embodiment, the method does not merely determine a break in the track segment based on reduced current flow through all or a portion of the track segment. Optionally, transmitting data indicative of a break can include transmitting an alert of a break and/or transmitting data of or relating to the phase angle between the at least two frequencies such that a determination of a break can be determined. Transmitting data indicative of a break can include transmitting data via a radio frequency of less than about 200 kilohertz. The method can also include monitoring a voltage of the at least two frequencies of alternating electrical current and using data from the monitored voltage to cancel out common parasitic resistance of the shunted segment of the track. 
     The method can also include relaying data received from an apparatus that is configured to monitor a different track segment. The method can also include providing a communication node that is configured to receive data from a plurality of monitoring devices, and/or transmitting data indicative of a presence of a vehicle on the track segment. The vehicle can be a train or portion thereof and the track can be a rail track. 
     Embodiments of the present invention also relate to a method for detecting a condition of rail tracks that includes forming segments of the rail tracks by coupling shunts between rails of the rail tracks at intervals, providing a plurality of detectors and coupling a respective one of the plurality of detectors to a respective one of the formed segments of rail tracks, providing at least two frequencies of alternating electrical current to the respective one of the formed segments of rail tracks, evaluating a change in signal amplitude above a baseline reference in at least one of the at least two frequencies, and evaluating a phase angle difference between the at least two frequencies of alternating electrical current; and detecting the condition based on a change in the signal amplitude and phase angle difference between the at least two frequencies. The shunts can include wires and/or cables. The shunts can include filters that are tuned to pass operating frequencies but attenuate other frequencies, which other frequencies can optionally include direct current. In one embodiment, a bypass can be formed in a section of rail tracks by disposing the shunts on either side and/or both sides of the bypass section and not disposing a detector in the bypassed section. Forming a bypass section can include forming a bypass section at or near a location of rail equipment such that the rail equipment lies within the formed bypass section. The rail equipment can include a wheel condition detector. In one embodiment, axles of all moving trains move with respect to the plurality of detectors. In one embodiment of the method, the condition can include a rail switch position, a break in a portion of the rail tracks, and/or a train presence condition when a train is disposed on at least one of the segments of the rail tracks. Detecting the train presence condition can include detecting a negative amplitude shift for the at least two frequencies in addition to a positive phase shift for the at least two frequencies. 
     Optionally, detecting a break condition can include detecting the break when a positive amplitude shift relative to an amplitude of a higher of at the at least two frequencies from the baseline reference is observed in a lower of the at least two frequencies of alternating electrical current in combination with a negative phase shift relative to a phase shift of a lower of the at least two frequencies in a higher of the at least two frequencies of alternating electrical current. 
     The baseline reference can be compensated for environmental effects by normalizing signal amplitude values relative to phase values when no trains are present and when no breaks are present. Optionally, the detected condition can include a change in rail stress, which stress change can be formed in response to a break in at least one of the segments of rail tracks at a location other than a segment of the rail tracks where the rail stress is detected. The rail stress can be formed by thermal expansion and/or thermal contraction of the rails of the rail tracks. 
     Embodiments of the present invention also relate to a detector that includes a circuit configured to provide at least two frequencies of alternating electrical current to a shunted segment of a track, the circuit configured to measure an amplitude difference and a phase angle between the at least two frequencies of alternating electrical current and identify a break in at least a portion of the track based on a change in the measured amplitude difference and phase angle, and the detector not disposed on a train or moving vehicle. In one embodiment, the detector does not travel with respect to the shunted segment of the track while the detector is in operation. The circuit can provide the at least two frequencies of alternating electrical current via a direct electrical connection to rails of the shunted segment of the track and/or via induction into a rail of the shunted segment of the track. The circuit can be configured to measure via direct electrical connection to rails of the shunted segment of the track and/or via induction into a rail of the shunted segment of the track. The detector can also include an isolation transformer. Optionally, the circuit can be configured to provide at least two frequencies of alternating electrical current into two shunted segments of a track. The two shunted segments of a track can include two adjacent segments of a track. The amplitude difference can include a difference between a current amplitude and a reference amplitude. The phase angle between the at least two frequencies of alternating electrical current can include a difference between a current phase and a reference phase. 
     Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more embodiments of the invention and are not to be construed as limiting the invention. In the drawings: 
         FIG. 1A  is a drawing which schematically illustrates a broken rail detector according to an embodiment of the present invention; 
         FIG. 1B  is a drawing which illustrates a length of rail tracks that are monitored by a plurality of nodes and which communicate information to a communication node according to an embodiment of the present invention; 
         FIG. 2  is a drawing which schematically illustrates an electrical equivalent of a shunted portion of railroad tracks; 
         FIG. 3A  is a drawing which illustrates a test setup wherein an embodiment of the present invention was constructed and tested in a lab; 
         FIG. 3B  is a drawing which illustrates the area of the test setup wherein the electrical connection was made on one of the rails for the connection of the electrical components; 
         FIG. 4A  is a drawing which schematically illustrates a broken rail detector that is configured to inductively couple to rails via parallel conductors; 
         FIG. 4B  is a drawing which schematically illustrates a broken rail detector that is configured to inductively couple to rails via coils; 
         FIG. 4C  is a drawing which illustrates an inductive coil configuration according to an embodiment of the present invention; 
         FIG. 5A  is a drawing which illustrates a configuration wherein signals are input into rails via injection shunts and wherein a pair of adjacent segments are monitored by remotely positioned signal detectors; and 
         FIG. 5B  is a drawing which illustrates a configuration for a signal detection-portion of a detector according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention detect breaks in a track, such as a rail track, and detects the presence of a train, train car or other rail vehicle on a portion of the track, by treating a portion of the track as a long conductor. As such it has two dominant properties, resistance and inductance. Reliance on a change in resistance, caused by a break in the rail (conductor) is commonly used in existing technologies. This property is subject to the effects of rail contamination that allows current to leak into the earth, through dirt and moisture, and bypass the break. Special procedures are required to mitigate this problem. 
     Referring now to the figures, detector  10  preferably takes advantage of the inductive properties of rail tracks  12  and cancels out the environmental effects. To achieve this, rail tracks  12 , which are preferably formed from a plurality of individual rails  14  arranged in parallel and disposed a distance from one another, are preferably electrically shunted together via track-to-track shunts  16 . Shunts  16  preferably include, for example, a wire connected between a pair of rails  14 . Although shunts can comprise almost any desired size or diameter, in one embodiment, shunts  16  most preferably comprise about 20 gauge to about 8 gauge wire and more preferably about 16 gauge to 12 gauge wire and most preferably about 14 gauge wire. Although the connection of shunts  16  can be made at any desirable location or configuration, in one embodiment, shunts  16  are most preferably permanently bonded to the web or foot of the rail. Shunts  16  are most preferably formed from a stranded steel cable, but can be formed from other materials and structures, and can optionally include existing connections—for example, shunted connections associated with existing infrastructure, which can include for example portions of warning circuits associated with active crossing warning systems. Most preferably, a plurality of shunts  16  are disposed along rail tracks  12  at a predetermined distance interval (See  FIG. 1A ). The predetermined distance interval can optionally be made large—for example greater than 100 feet, more preferably greater than 1,000 feet, and most preferably about one mile or more. At some point between a pair of shunts  16 , which can include for example near a mid-point of the distance between a pair of shunts  16 , a connection is made to each rail  14  and a signal generator  18 , which is preferably equipped with or otherwise coupled to a current sensor  20 , which can include for example, a voltage measurement taken across a known resistance, which itself can include a measurement across resistor  21 . Although in one embodiment, connection is most preferably made at or near a mid-point of a segment of rail tracks  12 , in one embodiment, the apparatus and method can provide desirable results when connection is made anywhere from about ¼ to about ¾ of the length of a rail segment. 
       FIG. 2  illustrates an electrical equivalent circuit of the configuration formed by detector  10 . As can be seen, electrically, the shunted portion of rails  14  behave as parallel inductors, first loop  22 , and second loop  24 , when signal generator  18  and current sensor  20  (see  FIG. 1A ) are connected thereto, thus providing unknown parasitic resistance  26  in first loop  22 , which is in parallel with rail inductance  27 , and in second loop  24 , unknown parasitic resistance  28  which is in parallel with rail inductance  29 . Parasitic resistances  26  and  28  are caused by environmental contamination of the rails, usually from combinations of dirt, rain, snow, standing water, etc. Environmental effects also occur from heating and cooling cycles during the day as well as resistivity changes at bolted joints. Signal generator  18  preferably applies an electrical signal to rails  14 . Most preferably the signal applied is a relatively low frequency—for example, less than 100K Hertz (“Hz”) and most preferably less than 10K Hz. Optionally, the frequency can be less than 1K Hz and/or less than 100 Hz. 
     The signal detected at point  30  of  FIG. 1A  is preferably measured for both amplitude and phase relative to the signal measured at point  32 . The signal detected and/or measured at points  30  and  32  are preferably made with respect to common point  34 . Optionally, a section of track can be divided into segments and each segment can be monitored via an embodiment of the present invention and a circuit for monitoring each segment is occasionally referred to herein as a “node” such that a length of track is monitored by a plurality of nodes. Signal injection and detection points  36  and  37  together serve as a monitoring point for a segment or section of rail tracks  12 . Thus, if a span of 100 miles of rail tracks were divided into 100 segments that were each one mile long, and if each segment had detection points  36  and  37 , there would thus be formed  100  nodes for that 100 miles of rail tracks. If a break occurs in either, or both, of first loop  22  and/or second loop  24 , the inductance presented at detection points  36  and  37  will change and there will be a resulting change in both the amplitude and phase of the signal detected at point  30 . This amplitude will also be affected by the amount of parasitic resistance that is present. It cannot be assumed that the parasitic resistance is constant or in any way predictable. By applying two different frequencies (for example 100 Hz and 500 Hz) to the rail loops, the common parasitic resistance can be cancelled out by measuring the ratio of the amplitudes of the two frequencies detected at point  30 . This assumes that the amplitude of both frequencies at point  32  is the same. If not, the signals measured at point  30  are preferably normalized accordingly. Further, the measured phase angle for each frequency can be used to detect the presence of a break. This can be done with a single frequency or multiple frequencies. With a single frequency, unknown parasitic factors can cause errors in the defect detection. Crossing control systems that use a method that operates on a single frequency, instead of a plurality of different frequencies as is preferably used in embodiments of the present invention, must operate at fairly high power levels (10&#39;s of watts), and over comparatively short lengths of several hundred feet; whereas embodiments of the present invention were tested and found to provide desirable results using only about 1 watt of power to perform a test sequence on a 1-mile section of rail. 
     The ratio of the phase angles between the two frequencies can be used to further improve accuracy of the break detection. A simplified example of this process is illustrated in the measured test data of Tables 1 and 2 as further discussed in the Example 1 below. 
     As can clearly be seen in the example data of Tables 1 and 2, there is a change in inductance associated with a rail break condition. Conversely, the presence of a train in the monitored section of rail tracks  12  causes a corresponding reduction in the measured inductance value as the train wheels and axles create shorter conductor loops by shunting the rails at positions closer to the detection point. 
     The rail shunts also act to isolate track sections. Using the measurement methodology described above, rail break and train presence events that occur before the left shunt or after the right shunt are not detected. This allows a detection event to be positively associated with a section of rail monitored by a given node. If the measurement point is not centered in the monitored rail section it is possible to determine which side of the node the detection event occurred on. 
     During a normal test sequence, only a small number of cycles (for example, about 10 or less) of each frequency are required to complete a detection test. This enables testing to be performed very rapidly, thus resulting in nearly instantaneous testing of an entire section of rail tracks  12 . 
     Data communication module  40  is preferably communicably coupled to detection points  30 ,  32 , and  34  and can thus communicate to a hub or other location, measured results and other data (for example a status indicator, which can include for example the detection of an improperly functioning circuit and/or a low or loss of power indicator). 
     In one embodiment, data communication module  40  can include a node box which has space to mount a variety of data telemetry technologies. As such, each data communication module  40  can accommodate any of various data telemetry systems. Such various data telemetry systems can include not only low frequency RF communications, but can optionally include, in rail data transmission, conventional radio-based modems, cellular systems, satellite, fiber optic, internet-based, conventional telephone lines, combinations thereof and the like, as well as any other known data transmission protocols and/or systems. For example, rail tracks which pass from a vast open area through a city and back through an expanse of open area can optionally include low frequency RF data transmission in the open areas but can include cellular and Internet data transmission along portions of the rail tracks that pass through a city. Thus, a single length of rail tracks can be monitored and the data generated thereby can be transmitted by a combination of different communication systems and/or protocols. This flexibility allows the telemetry hardware to be tailored to various environments. 
     Optionally, a daisy chain communication system can be used. Also optionally, each data communication module  40  can have a unique identification (i.e. a “node ID”), and/or a mile marker indicia. Each communication node  50  can optionally have a table of the unique identifications of the various data communication modules and also preferably of their corresponding mile marker indicia, in a monitored subdivision. 
     Data can be transmitted as messages and can optionally include an identification sequence number in addition to the node ID and mile marker indicia for the node that sourced the message. Each message also preferably contains the node ID and mile marker indicia of the node that relayed the message. These values can be the same as the source node for the first relay. When a node broadcasts a message (i.e. when data communication module  40  broadcasts a message), it can be detected by the data communication module of one or more adjacent nodes. 
     The telemetry logic is preferably configured so that a message from a data communication module can be transmitted sequentially (for example node-by-node in each direction), thus resulting in ascending and descending node and mile marker indicia. Optionally, confirmation of a received message can be sent back to the previous node before being passed on to the next node. This methodology allows corrupted or lost transmissions to be retried. Still further, sending the data in both directions allows the message to reach at least one communication node  50 , and likely two. Optionally there can be more than one communication node  50  in any given sub-division of rail tracks. In one embodiment, one or more, or even all data communication modules  40  can optionally be configured to communicate directly with one or more communication nodes  50 , without requiring the data to be relayed through other data communication modules. This can be particularly advantageous in urban areas with a significant amount of existing communication infrastructure. 
     When a broken rail or train presence event is detected, it is preferably communicated to a data hub or a central location so that the appropriate action can be taken. The railroad environment is highly varied and does not generally allow for the consistent application of radio or other communication methods without a considerable investment in supporting infrastructure. Controlled crossings and urban rail sections often already have this infrastructure in place. Rail lines in rural or remote areas may only have communication capabilities at controlled crossings or at specific sections of instrumented track. Un-monitored rail sections are referred to as dark territory. 
     Embodiments of detector  10  preferably do not require the construction of additional communication infrastructure to each detector for each segment of rail tracks  12 . Instead, low frequency radio waves are preferably used to communicate between detectors. Optionally, a rail can be used as a conductor for long wavelength electromagnetic signals or as an antenna when an insulated rail joint is encountered—for example, as are used for some types of controlled crossings. 
     Low frequency radio communication is rarely used now due to its very low data rate capabilities and the typically very long antennas that are needed, which can exceed 1000 feet in length. Using the rail itself as an antenna or signal conductor solves this problem. Remote car starters and key ‘fobs’ commonly use this frequency band but do not operate at the power levels required to interfere with the signals used in data communication module  40 . 
     Optionally, a length of rail tracks  12  can be divided into a plurality of monitored segments which are each monitored by a separate detector  10 . Optionally, detectors  10  can be placed at intervals of approximately 1 mile along a section of rail tracks  12  to be monitored. Each detector  10  is preferably independently powered and operates independently of other detectors for other segments of rail tracks  12 . It is possible that more than 100 detectors can form a group monitoring a section of rail tracks  12 . A monitored section of rail tracks  12  is occasionally referred to herein as a “sub-division”. Over the course of several monitored segments (for example over the course of 100 miles), there can be a point where a preexisting data communication point exists (for example a ‘Hot-Box’, which can be provided for example at a monitored crossing). At this point, communication node  50 , (see  FIG. 1B ) which can optionally include a detector  10  (which if provided can also monitor a segment of rail tracks  12 ), can be placed. Regardless of whether a communication node  50  is connected to an accompanying detector for that particular segment of rail tracks  12 , communication node  50  preferably communicates with the other detectors  10  by passing data from detector  10  to detector  10  (or at least the data communication module  40  thereof) along the monitored section of rail tracks  12 . As such, data communication module  40  can be configured to relay communications received from other detectors  10 , such that data from one detector is relayed through the communication module  40  of other detectors  10  until the data finally reaches communication node  50  where it can be transmitted (for example where it can be transmitted via previously installed communications infrastructure). This methodology is generally much less susceptible to environmental effects such as line-of-sight, snow cover, foliage effects, and interference of other common radio technologies. 
     The data communication method used by embodiments of the present invention requires very low power at each detector  10  and allows each detector to optionally be powered by a battery with a small solar panel for recharging. Very low power consumption is required for areas where there are extended periods of low light levels (for example northern areas) or when detectors  10  are covered by snow. 
     With respect to the inter-node data communications system that is preferably implemented via data communication module  40 , terrain problems can include line-of-sight obstructions, foliage absorption and snow cover, which can limit the use of very high frequency and microwave bands of radio telemetry. A low frequency radio band can be used and will provide desirable results. Most preferably, data communication module  40  transmits, receives, and/or relays data at a about 10 Khz to 500 Khz and more preferably at about 50 kHz to about 200 kHz frequency range. Telemetry power consumption is most preferably less than about 0.2 watts and more preferably less than about 0.08 watts in the receive mode. In one embodiment, communication module  40  can transmit and/or relay data at a rate of about 100 to about 2,000 bits per second and more preferably at a rate of about 500 bits per second. 
     In one embodiment, a rail break is determined when a positive amplitude shift from a baseline reference point is observed in a lower test frequency while a negative phase shift is observed in a higher test frequency. In one embodiment, a train presence is determined when a negative amplitude shift is observed in addition to a positive phase shift for all frequencies. In one embodiment, the baseline reference level is preferably compensated for environmental effects by normalizing the amplitude values relative to the phase values when no trains are present and when no break defects are present. 
     In one embodiment, a break and/or train presence can be determined by amplitude and/or phase relationship between at least two frequencies. In one embodiment, shunts  16  can be simple wires connecting rails  14  to form the shunted rail loop. Optionally, however, shunts  16  can be an electrical filter that is tuned to passes the operating frequencies but attenuate or block other frequencies, which can optionally include direct current that may or may not be associated with other equipment or instruments that are electrically connected to rail tracks  12 . 
     Optionally, shunts  16  can be used to bypass sections of a rail that contain switches, crossings, rail frogs (an intersection between 2 rails) or any other desired area. In this embodiment, shunts  16  are preferably installed across rails  14  on both sides of the equipment, thus forming a track segment that contains the equipment. However, a detector circuit is preferably not disposed in the segment containing the equipment. This same isolation configuration can be used to isolate wheel condition detectors, or other devices that may interfere with operation of detector  10 . In addition, the same isolation technique can be used to isolate any equipment that may be adversely affected by normal operation of detector  10 . 
     In one embodiment, train presence can be determined by conductive train axles causing a moving shunt that acts to change the properties of the monitored track loop. When detector  10  is in operation, the length of the rail loops on each side of the connection point are fixed. This means that for any given set of environmental characteristics the ratio of inductance between the left and right loops is constant. When a train axle is present, it acts to shorten one of the rail loops as it enters the monitored section. This in turn reduces the inductance of the entry loop and changes the ratio of inductance between the left and right loop. The characteristics of this change are detected by detector  10 . As the train continues into the monitored section, the first rail loop length is reduced to zero when the train is adjacent to the connection point of detector  10 . Many, if not most, freight trains are now of great length and may simultaneously occupy two or more monitored sections of rail tracks  12 . So long as the train axles are in the immediate proximity of the connection point, the loop lengths, both on the entry and exit sides of the monitored area, are at or near zero. As the last axle of the train moves past the connection point, the entry loop length has returned to its original length and inductance characteristics while the loop on the exit side is starting at zero length and is now becoming longer, eventually returning to its original length and inductance characteristics. The changes in the inductance ratios between the entry and exit loops can be used to determine the location of the axles in the monitored sections of rail tracks  12 . Furthermore, by correlation of the data from adjacent monitored sections, the location of the front and rear, as well speed and direction, can be determined by detector  10 . 
     Rail switch position can optionally be detected by monitoring the change in electrical properties of the monitored loop. These changes are caused by the movement of the rail switch machinery. For example, in one embodiment, the change in rail switch position can change the effective length of a loop that is monitored by detector  10 , thus enabling detector  10  to detect the switch position and report it periodically or when queried for position status. 
     In one embodiment, rail breaks can be detected by changes in the monitored loop that are caused by the change of rail stress which occurs when a break is created in an adjacent or near-by track section. This effect can extend for several miles and can be detected by several detectors  10  positioned along several sections of rail tracks  12 . A change in rail stress as a function of temperature can also be determined by changes in the rail electrical properties that are the result of structural strain in the monitored rail section. Typically, when a rail break occurs there is a frequency dependent change in the inductance properties of adjacent, connected, rail sections. This effect appears to extend for between about two to about four miles on either side of the break. The effect decreases as distance from the break increases. This effect allows for the determination of an approximate location for the break. This can be useful for determining if a break has occurred in an unmonitored area (for example, in a controlled crossing or bridge), that is between two or more monitored sections. The characteristic response often lasts for several minutes before typically recovering to near the original state. Extracting the information can be performed by analyzing data from several adjacent sections and checking for the characteristic signature occurring at the same time at two or more monitored sections of rail tracks  12 . This further illustrates the ability of a plurality of detectors  10  operating as part of an extended array. 
     Train location in a monitored section of rail tracks  12  can be determined by measuring the change in amplitude and/or phase of the generated signals. Changes in the amplitude and phase of the generated signals occurs as the train moves through the monitored section and causes the electrical length of the rail loop change. This follows a predictable profile and allows the train location in the loop to be determined. These characteristics also allow the approximate speed of the train to be determined using detector  10 . The measured frequencies can be introduced into the rail by direct or indirect methods. Direct introduction of the generated frequencies can be done by wire connections directly to the rails, most preferably at the approximate midpoint of the rail loop. It has been found that a desirable attachment range is about +/−30% of the rail loop length relative to the center point of the section of rail tracks  12 . Indirect introduction of the frequencies can be done by induction. For example, this can be done by placing a length of wire parallel to a rail that forms part of the monitored rail loop. A current passed through the wire operating at the measured frequencies. The magnetic field created by this current flow induces a current of the same frequency in the monitored loop section. 
     Sensing of the electrical currents can likewise be determined by either direct or indirect connection to the rails of the monitored loop section. In this embodiment, direct measurement of the generated frequencies can be done by wire connections directly to the rails, most preferably at the approximate midpoint of the section (see  FIG. 1A ). It has been found that a desirable attachment range for this connection is also about +/−30% of the rail loop length relative to the center point of the loop. The connection of the signal measurement equipment can but does not need to be coincident with the frequency generating equipment. Likewise, indirect measurement of the generated frequencies can also be done inductively (see  FIG. 4A ). This can be done by placing a length of wire  60  parallel to a rail that forms part of the monitored section of rail tracks  12 . In this configuration, wire  60  functions as a receive wire to inductively pick up electrical signals flowing through the rail inductively. A current passed through the adjacent rail generates a time varying magnetic field that generates a voltage in the adjacent monitoring wire. In the parallel wire configuration, the parallel wire acts in the same manner as coaxial coils in an air core inductor. Likewise, the electrical signals can be injected into rail tracks  12  inductively as illustrated in  FIG. 4A . In this embodiment, a length of wire  62  is placed along rail  14  and the signal is applied to wire  62 , thus causing wire  62  to be a drive wire and induce a signal into the adjacent rail. Most preferably, drive wire  62  is positioned to drive one of rails  14  while receive wire  60  is positioned to monitor another rail  14 . Wires  60  and/or  62  need not be parallel with their respective rails. Rather, any shape and position which enables induction between the wire and rail  14  can be used. For example, wires  60  and/or  62  can be wound into coils  64  and/or  65  (see  FIGS. 4A and 4B ). Likewise, wires  62  can be wound into coil  65 , and a core  66  can be shaped to provide better inductive coupling between coil  64  and rail  14 . In one embodiment, core  66  can comprise a laminated iron core and/or ferrite core and can optionally have a C-shape which partially encircles a bottom portion of rail  14 . For embodiments wherein the signal is injected into the rails inductively and/or detected via induction, a single detection loop is formed in a rail segment. This is because a break to either side of the injection/detection points will result in changes to the received signal. 
     For this embodiment there is most preferably one wire against one rail (but electrically insulated from the rail). This serves as the signal driver and induces an electrical current into the rail. This process follows Faraday&#39;s law of inductance. The receiver is preferably coupled on another rail but can be coupled at any point in the rail loop. In this configuration the system behaves as a single loop. All the principles of break detection still apply. 
     The generated operating frequencies can be part of a frequency cycle, a single cycle or multiple cycles. The operating frequencies can be generated consecutively or be mixed into a combined waveform. Circuitry in the detection electronics can be used to extract amplitude and phase information for each of the generated frequencies. In order to accomplish this, in one embodiment, no circuitry modifications are required. Rather, this can be implemented in firmware to demultiplex the received signals back into the separate frequencies. Signals to and from the rail can optionally be connected by a combination of direct and indirect methods. Transformer  70 , which can be an isolation transformer, can optionally be used. In this embodiment, one winding of transformer  70  is preferably attached to the signal generation circuit, or the signal monitoring circuit, and the other side of the transformer is electrically connected to rail  14 . In one embodiment, the transformer  70  (see  FIG. 5A ) can be a 1:1 ratio or it can be a step-up or a step-down transformer. For example, in one embodiment, isolation transformer  70  can comprise a step-down configuration for impedance matching for signal injection into the rail while another isolation transformer  70  can comprise a step-up configuration for passive signal amplification and impedance matching for signal detection. In this configuration, the receive side can then be followed by active signal filtering and amplification. Note that  FIG. 5A  is not drawn to scale as in a most preferred embodiment, the distance between adjoining rails  14  is preferably significantly closer together than the distance between shunts  16  and injection shunts  78 . As best illustrated in  FIGS. 5A and 5B , in one embodiment, signal generator  18  can be located at or near a shunt location that forms the end portion for two adjacent monitored sections of rail tracks  12 . The output can be split to drive the injection signal for the two adjacent rail segments simultaneously. In this configuration there is preferably a single signal generator  18  driving two monitored rail segments (the portions from injection shunt  78  to an adjacent shunt  16 ). In this embodiment, injection shunt  78  is preferably configured such that a second winding of isolation transformer  70  is preferably in series with injection shunt  78 . Signal detectors  80  are preferably coupled to detector  10  via connection cable  82 . Most preferably, signal detectors  80  are disposed at or near a central portion rail  14  on both sides of detector  10  so as to enable monitoring of both adjacent rail sections where detector  10  is disposed. In one embodiment, signal detectors  80  can be inductively coupled as previously described, or signal detectors  80  can each comprise two wires which can connect to a respective one of rails  14 . In one embodiment, signal generator  18  can be coupled to isolation transformer  70  for injecting a signal with intervening drive amplifier  84 . This enables the injection signal from signal generator  18  to be amplified to any desirable level. Optionally, the connection from signal detectors  80  to detector  10  can be made inside the node, for example, detector  10  can be spatially split apart such that the portions of detector  10  which are responsible for signal injection (injection portion  86 ) can be disposed at or near injection shunt  78 , while portions for detection and data processing and transmission can be disposed at or near a center portion of each segment of rail to be monitored. In this embodiment, signal generator portion  18  can optionally provide the detection portion of detector  10  with a reference signal so that the signal detection portion of detector  10  will have accurate information on the injection signal. In one embodiment, this can be done by providing a direct physical electrical connection between the signal detection portion of detector  10  and the signal injection portion of detector  10 . Alternatively, however, the signal injection portion can wirelessly transmit the injection signal to the receiver portion of detector  10 . 
     As best illustrated in  FIG. 5B , data processor  76  is preferably provided. Optionally data processor  76  can be incorporated with the rest of the electronics of detector  10 , or data processor  76  can be a separate unit which receives and process data apart from the rest of detector  10 . Most preferably, data processor  76  acquires the data and processes it to produce the results that are to be transmitted from the detector  10 . For the embodiment wherein injection portion  86  is spatially separate from detection portion of detector  10 , signal lines from injection portion  86  preferably provide timing reference information to processor  76  so that processor  76  can perform analysis as described in more detail above to detect train presence, rail break, and/or any of the other detections previously described. Processor  76  can then send information to communication module  40  to be transmitted. 
     An embodiment of the present invention uses signals for rail break detection, train presence detection and data communication that are at frequencies and power levels that are highly unlikely to affect existing signaling and other infrastructures that are normally present on an operating track. In one embodiment, detector  10  is not disposed on a train. Instead, a plurality of detectors are preferably provided and connected such that each detector is coupled to a respective track segment. Embodiments of the present invention preferably do not depend on direct current (“DC”) or alternating current (“AC”) current methods that detect rail breaks by loss of current flow as such methods are subject to false results created by environmental rail-to-rail and rail-to-earth leakage. Because detector  10  is preferably stationary and trains approach pass by detector  10 , in one embodiment, the axles of every moving train move with respect to detector  10 . 
     INDUSTRIAL APPLICABILITY 
     The invention is further illustrated by the following non-limiting examples. 
     Example 1 
     A portion of a test rail track was constructed along with an apparatus according to an embodiment of the present invention (see  FIGS. 3A and 3B ). 
     This first test was setup to test a broken rail detector using a 40-foot test rail in a test laboratory, in order to evaluate parallel inductive loops that are formed in the test rail. The equipment used in the test included, the test rail, a frequency generator, an oscilloscope, an inductance meter, a digital voltmeter, and a current sense resistor. A schematic of the test setup is illustrated in  FIG. 1A . For the test, resistor  21  was used and had a value of 60 ohms. Point  32  was connected to channel A of the oscilloscope. Point  30  was connected to channel B of the oscilloscope. The signal generator was used without additional amplification. 
     Table 1 summarizes measurements taken when no break was provided in the rails. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Frequency 
                 Gen. Amplitude 
                 Rail Amplitude 
                 Phase Delay  
               
               
                   
                 (kHz) 
                 (V p-p) 
                 (V p-p) 
                 (μS) 
               
               
                   
                   
               
             
            
               
                   
                 150.00 
                 2.0 
                 0.28 
                 −0.95 
               
               
                   
                  49.69 
                 2.0 
                 0.13 
                 −3.0  
               
               
                   
                   
               
            
           
         
       
     
     Table 2 summarizes measurements taken when a break was provided in one of the rails. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Frequency 
                 Gen. Amplitude 
                 Rail Amplitude 
                 Phase Delay  
               
               
                   
                 (kHz) 
                 (V p-p) 
                 (V p-p) 
                 (μS) 
               
               
                   
                   
               
             
            
               
                   
                 150.38 
                 2.0 
                 0.48 
                 −0.75 
               
               
                   
                  49.69 
                 2.0 
                 0.31 
                 −2.0  
               
               
                   
                   
               
            
           
         
       
     
     Given the greater than 400:1 ratio between the rail loop resistance and the signal injection series resistor, less than 0.005V of the rail amplitude value can be attributed to changes in the DC resistance of the test track when it was broken. As previously noted, the DC resistance was below measurable limits under both break and no-break conditions. 
     Environmental rail-to-rail and rail-to-earth leakage was not simulated in this test but would not likely appear as a ratio change in the signal rail amplitudes; instead it would appear as a change in absolute signal value. Therefore, two widely separated signal frequencies are preferably used. Changes in inductance manifest as a change in the ratio of the amplitudes and phase shift of the two test frequencies. The amplitude ratio between frequencies for no break was found to be 2.15, while the amplitude ratio between frequencies for a break was found to be 1.54. Likewise, the phase ratio between frequencies for no break was found to be 0.32, while the phase ratio between frequencies for a break was found to be 0.38. The phase ratio for 150 kHz between break and no break conditions was found to be 1.27, while the phase ratio for 50 kHz between break and no break conditions was found to be 1.5. Thus, it was found that there was a very clear response in the measurements achieved between the break and no break conditions. 
     Example 2 
     After the successful test of Example 1 above, an embodiment of the present invention was constructed and tested on live track test sections that were up to two miles long. Rail break and train presence detection was tested and found to work as described. The described method for compensating for environmental effects was also tested and found to perform well. For this test, the following equipment was used: a PicoScope digital oscilloscope, a 15 watt (“W”) linear audio power amplifier, three 1.5-ohm power resistors; a portable generator (for field power), clip leads, a FLUKE® (a registered trademark of Fluke Corporation) model 77 multimeter, a Brunelle 3200 LC meter, and a signal generator. The response of signal amplitude and phase to train presence and simulated rail break, shunt removal in this case, was consistent with expectations. 
     The test setup was connected as schematically illustrated in  FIG. 1A . For the test, the resistor had a value of 5.2 ohms. Point  32  of the schematic of  FIG. 1A  was connected to channel A of the oscilloscope, while point  30  was connected to channel B of the oscilloscope. The signal generator included a 15-watt amplifier being driven from a signal generator. The 5.2 ohm series resistors used were rated at 50 W. The 15 W linear amplifier was used to drive the rail. Shunt 1 was in place at mile 96.5, while the test site was at mile 97.0. This shunt was a permanent shunt associated with existing crossing detection equipment. 
     Because it was impractical to intentionally create a break in an active section of track, we instead removed one of the shunts to simulate a break. Table 4 shows the results of tests when the break was simulated. The following values were measured/determined: 
     1) Initial DCR=˜0.2 ohm 
     2) Shunt 2 was placed at mile 97.5. 
     3) Inductance was 12.6 mH 
     4) DCR=˜0.2 ohm 
     5) Difference with shunt in and shunt out. Voltage differential was calculated as: 
       dV i =VA—VB for shunt in
 
       dV o =VA—VB for shunt out
 
         d Phase=Phase Delay In −Phase Delay Out
 
       dV==dV i −dV o  
 
     Table 3 shows the results of tests when both shunts were in place while Table 4 shows the results of tests when shunt 2 was removed to simulate a broken rail. Table 5 shows the results of the comparison of the unbroken track segment and the simulated broken segment. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Voltage at  
                 Voltage at  
                 Phase Delay at  
               
               
                   
                 Frequency 
                 Test Point A 
                 Test Point B 
                 Test Point B 
               
               
                   
                 (Hz) 
                 (Vp-p) 
                 (Vp-p) 
                 (uS) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 150 
                 19.30 
                 6.11 
                 371.8 
               
               
                   
                 300 
                 19.57 
                 6.52 
                 304.5 
               
               
                   
                 1000 
                 19.69 
                 10.72 
                 66.2 
               
               
                   
                 4000 
                 19.69 
                 13.40 
                 8.6 
               
               
                   
                 10000 
                 19.66 
                 14.81 
                 2.6 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                 Voltage at  
                 Voltage at  
                 Phase Delay at  
               
               
                   
                 Frequency 
                 Test Point A 
                 Test Point B 
                 Test Point B 
               
               
                   
                 (Hz) 
                 (Vp-p) 
                 (Vp-p) 
                 (uS) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 150 
                 19.37 
                 7.05 
                 330.8 
               
               
                   
                 300 
                 19.56 
                 7.41 
                 262.9 
               
               
                   
                 1000 
                 19.53 
                 10.41 
                 46.9 
               
               
                   
                 4000 
                 19.48 
                 13.30 
                 9.1 
               
               
                   
                 10000 
                 19.46 
                 15.04 
                 2.3 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Frequency 
                 dVi 
                 dVo 
                 dV 
                 dPhase 
               
               
                   
                 (Hz) 
                 (V) 
                 (V) 
                 (V) 
                 (us) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 150 
                 13.19 
                 12.32 
                 0.87 
                 41.0 
               
               
                   
                 300 
                 13.05 
                 12.15 
                 0.90 
                 41.6 
               
               
                   
                 1000 
                 8.97 
                 9.12 
                 −0.15 
                 19.3 
               
               
                   
                 4000 
                 6.29 
                 6.18 
                 0.11 
                 −0.5 
               
               
                   
                 10000 
                 4.85 
                 4.42 
                 0.43 
                 0.3 
               
               
                   
                   
               
            
           
         
       
     
     During the test, a clearly measurable difference in voltage and/or phase was noted at most frequencies—thus indicating that the concept of the invention is valid. Tests were also done with shunt 2 placed at about mile 98.5, thus creating a span of two miles between shunt 1 and shunt 2. A difference was noted at each of 1000 Hz and 300 Hz but there was not time to capture the detailed data due to an oncoming train. Train presence showed the expected opposite trends in voltage and phase at 300 Hz, with a clear downward trend as the train approached the test location and an increasing trend as it left the test location. The tests clearly indicated the ability to detect both rail break and train presence conditions. 
     The preceding example can be repeated with similar success by substituting the generically or specifically described components and/or operating conditions of embodiments of the present invention for those used in the preceding examples. 
     Optionally, embodiments of the present invention can include a general or specific purpose computer or distributed system programmed with computer software implementing steps described above, which computer software may be in any appropriate computer language, including but not limited to C++, FORTRAN, BASIC, Java, Python, Linux, assembly language, microcode, distributed programming languages, etc. All computer software can be embodied on any non-transitory computer-readable medium (including combinations of mediums), including without limitation CD-ROMs, DVD-ROMs, hard drives (local or network storage device), USB keys, other removable drives, ROM, and firmware. 
     The apparatus may also include a plurality of such computers/distributed systems (e.g., connected over the Internet and/or one or more intranets) in a variety of hardware implementations. For example, data processing can be performed by an appropriately programmed microprocessor, computing cloud, Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or the like, in conjunction with appropriate memory, network, and bus elements. One or more processors and/or microcontrollers can operate via instructions of the computer code and the software is preferably stored on one or more tangible non-transitive memory-storage devices. 
     Note that in the specification and claims, “about” or “approximately” means within twenty percent (20%) of the amount or value given. 
     Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been described in detail with particular reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, none of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguring their relationships with one another.