So, audio frequency track circuits aftc were developed to over come the effect of ac induction in ac electrified tracks on conventional dc track. The audio frequency track circuit aftc is the jointless type of track circuit specifically designed to meet the onerous immunity required in ac or dc electrified areas against the high levels of interference present mainly due to traction harmonics. Because of the relatively high frequency, the signal quickly attenuates and, while pulse codes can travel for several miles, audio frequency. Basic doublerail power frequency track circuit 115 vac must be same source for both feeds fuse track transformer limiting resistor track relay pv250 insul. Pdf an audio frequency track circuit aftc, a recent addition to railway signalling, confirms the absence of a train in a section of track. Rse3h2 basic singlerail power frequency track circuit 3rd rail or. Its working length is dependent on immunity of track relay. Nrl3sig11761 issue 5 handbook for ebi track 200 audio. For additional information on pf track circuit key components, refer to these rse catalog sections. Ml ti21 af jointless track circuits set up, test and. Audio track circuit operation the principle of a track circuit is to detect the presence of a train by its wheelsets shorting out a signal transmitted along the rails to a distant receiver 7. Derby training centre or on a clients premises subject to suitable training rooms being available. The ac track circuit the ac track circuit is energized by an alternating electrical current with a frequency of 83.
Complete with rechargable batteries and multimeter test leads. Mar 05, 2010 an unoccupied track circuit is shown in diagram a. The joint less audio frequency track circuit aftc is the solution in such sections since they are immune to above interferences. Jul 21, 2010 this power point presentation of siemens and abb t21 audio frequency track. Dual code audio frequency track circuits and their use.
Sm 8051 technology drive, pittsburgh, pa 15219 645 russell street, batesburg, sc 29006. Ti21 audio frequency jointless track circuits, in a typical artc installation. Condition monitoring of track circuits may improve the availability of track circuits, hence improving service levels. Recommendation of service unit for siemens audio frequency track circuits and axle counters sico 2056 pega. They address the electrical components of the circuit emitter, receiver and lines, without accounting for the train component railwheel contact. Applicable for all clearguard ipitc series intelligent processor island track circuit module c6 clearguard ipitc series intelligent processor island track circuit module 9. Check that the transmitter power output is set correctly for the length of track circuit by selecting the appropriate transmitter tuning unit input terminals. Request sm6087 for pf track circuit component part numbers.
Complete rail solutions australian rail technology. In 4, distributive trackcircuit parameters were calculated using a semidiagonal matrix of. While pulsecoded track circuits have onoff cycles measured in pulses per minute, as their name implies, audiofrequency track circuits have signal frequencies in the range between 2 khz and 20 khz. Audio frequency overlay detector track circuit for electric propulsion territory 2 sheetssheet 1 filed may 6, 1965 kwkv oct. The receiver is connected to the rails at the far end of the track section and determines that the signal it receives is of the correct form, by performing fourier analysis of the signal. Maintenance handbook on audio frequency track circuit ver2 rdso. Us3345512a audio frequency overlay detector track circuit. A track circuit is a simple electrical device used to detect the presence or absence of a train on rail tracks, used to inform signallers and control relevant signals. In order for the system to work, tracks are divided into blocks of varying length. Af track circuit, audio frequency track circuit, hf track circuit, bond, impedance bond, signal, shunt, shunting device, track circuit.
The zepiciii is a 2wire audio overlay track circuit used by smartscan systems to sense train presence. Us4352475a audio frequency track circuit for rapid transit. Commissioning a new track circuit consists of removing any old equipment, connecting the new equipment and any new bonding, powering up the new equipment, then carrying out the final. Fail safe operation of audio frequency track circuits for railway. Most railroads use track circuits to determine which sections of track are occupied by trains.
Audio frequency track circuits linkedin slideshare. The smartway dtc is a solidstate, fail safe system which performs, in a safe way, the train detection, rail continuity detection and track to train data transmission functions within a track circuit tc using audio frequency signals. Track circuit reliability assessment for preventing railway. Audio frequency fs2500fs2600 track circuit applications. So, audio frequency track circuits aftc were developed to over come the effect of ac. Af902af904 generation ii audio frequency track circuit system. Zepic iii audio overlay track circuit southern technologies. The track circuit boards detect train location and apply the proper speed.
Condition monitoring of audio frequency track circuits. The transmitter modulates a track frequency carrier with a fixed code rate, regardless of the code rate employed to modulate the train information frequency. The unexpected high failure rate depleted existing inventory and left the system in danger of service disruption and safety risk. With the help of track circuit, one can easily identify whether the particular section is clear or occupied by a. Railway signalling track circuit railway signalling concepts. In 3, the jtcsignal frequency and phase were designed. The vti21 can be used to monitor fs2600 audio track circuits. Pdf fail safe operation of audio frequency track circuits. Evaluation of adequate maintenance staff requirements for corrective and preventative maintenance apta has developed this standard for use by any entity, public, or private, that regulates, inspects. This output consists of a lower frequency and an upper frequency which is modulated at. This standard provides procedures for inspecting and maintaining rail transit audio frequency track circuits. Aug 01, 2011 eventually became synchronized with the track circuit frequency. Us4352475a audio frequency track circuit for rapid.
Analysis of temperature impact on audio frequency track circuits. Mar 26, 2020 this output consists of a lower frequency and an upper frequency which is modulated at 15. Aptartssc00903 standard for audio frequency track circuit inspection and maintenance. The vti21 is capable of monitoring two fs2600 track circuits in parallel. This standard provides audio frequency track circuit tests that verify train detection shunting, and continued proper operation.
Oct, 2014 replace the damaged and corroded bonding wires. Spg 1057 audio frequency jointless track circuits for main line. Except for the type of current and apparatus used, the ac track circuit is similar in operation to the dc track circuit described above. Audio frequency track circuit free download as powerpoint presentation. An audio frequency track circuit aftc, a recent addition to railway signalling, confirms the absence of a train in a section of track. In railroading, this is called shunting the circuit. High power check that the receiver gain straps are preset tracks up to 400 metres. The completed circuit is shown in green on the diagram. Track circuit does not get shunted properly by vehicles.
Title specification audio frequency jointless track. Audio frequency track circuit power supply manufactured. Standard for audio frequency track circuit inspection and. To completely characterize the behavior of the track circuit under broken rail conditions, the operational characteristics of the track circuit must also be considered. The metropolitan atlanta rapid transit authority marta utilizes dual code audio frequency af track circuits to mitigate electromagnetic interference emi with the consequence of preventing the unsafe condition of falsely energizing track relays during track circuit occupancy. Introduction track circuit is a low powered electrical circuit in which running rails are used as a part. Dual code audio frequency track circuits and their use in vital train detection. These devices are actually fairly simple in design, and have been in use since 1872. In this paper a digital jointless af track circuit, operating in the 9. Failsafe is a familiar term to every signal maintainer and. Audio frequency track circuits competency australia. An audio frequency track circuit with improved security in the train detection function for rapid transit applications for use with uninsulated rails includes an improved transmitter and receiver.
These tests include recording the measured values for. The three standard code rates are 75, 120 and 180 cycles per minute. Track circuit reliability assessment for preventing. Failsafe is a familiar term to every signal maintainer and the participant in this series of training. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Do not test the track circuit by shunting with a wire only. If you continue browsing the site, you agree to the use of cookies on this website. In automatic signal territory, the controls for signals are accomplished by the use of various code rates in the coded track circuit. Audio frequency fs2500fs2600 track circuit applications overview the vti21 can be used to monitor fs2600 audio track circuits.
The audio amplifier will be a selfcontained, batteryoperated component. Handbook for ebi track 200 style t121 audio frequency track circuit the contents of this handbook apply to all ebi track 200 audio frequency track circuits. The unit also allows battery voltage measurement direct to the multimeter. This short course provides signalling maintainers and installers with the skills and knowledge to perform basic setup, maintenance and fault finding on bombardier ti21 ebi200 audio frequency track circuits. Af902af904 generation ii audio frequency track circuit. Pdf fail safe operation of audio frequency track circuits for. Provides consistent activation point independent of operating battery. This paper describes the instrumentation of a length of active track to. While pulsecoded track circuits have onoff cycles measured in pulses per minute, as their name implies, audio frequency track circuits have signal frequencies in the range between 2 khz and 20 khz. Audio frequency track circuit condition monitoring is a relatively new concept and little work has been done on the subject.
The more general requirements can be found in nrl2sig11752. A well prepared delegate is expected to be able to read circuit diagrams and have experience of working on a typical dc track circuit. Pickup time delay incorporate an integral time delay, to prevent energisation of the track relay during. While the basic concept is established, several issues. The audio frequency track circuit aftc is one of the most popular track circuit types. Their study is based on a labbased test rig of a single fs2550 audio frequency jointless track circuit.
This data is made available on the rs485 bus connected to a suitable mpec master logger typically an sa380tx. The transmitter modulates a track frequency carrier with a fixed code rate, regardless of the code rate employed to modulate the train information. The transmitter is the ac signal source and provides electrical energy at the operating frequency in the audiofrequency range. Plugs into a standard digital multimeter and has selectable frequency ranges and voltage levels. Audio frequency track circuit filter application part number filter to assist in the measurement of audio frequencies used in track circuits. As i pointed out last week, trains cant always stop within a lineofsight distance. Assessment of broken rail protection in audio frequency. In the second part of the lab you will construct a. Block and track circuit boundaries are defined by using impedance bonds, terminating receivers, or loops, or by insulated joints. For jtc, models of rail impedance and adjacent track interference were based on the. In ti21 jointless audio frequency track circuits, a carrier frequency f 0 is coupled into the track and detected at the receiver.
Field maintenance manual description installationand adjustment maintenanceand troubleshooting. The power source is located at the number 1, with the relay shown at number 2. Recognise the need for changing the shape of an amplifiers frequency response. Dual code audio frequency track circuits and their. Technofocus 2012, djscoe 89 audio frequency track circuit jinay vora 1, deesha trivedi 1 and ninad mehendale 2 1. The birmingham centre for rail research and education, department of electronic, electrical and computer engineering, the university of birmingham, birmingham, uk1. Audio frequency track circuits aftc modules the power amplifier boards on the existing segments 2 and 3 are failing at an alarming rate. Replaced sc 07 44 00 00 sp audio frequency jointless track. The transmitter generates a frequency shift keyed fsk signal which is fed to the rails at one end of a track circuit. So, audio frequency track circuits aftc were developed to over come the effect of ac induction in ac electrified tracks on conventional dc track circuits and also to avoid insulation block. Track circuits form a critical part of the uk rail signalling infrastructure.
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