The Evolution of Electronic Token Block for Railway Signalling
The origin of the electronic token block started in the late 1880s by Tyler & Co. with the development of the train tablet system. The main key operating principle of the electronic token block was having an instrument at each end of the section of the block electronically interlocked with each other and only one tablet could be withdrawn at a time and the tablet was given to the driver at his authority. In order to avoid the possibility of entering the token in the wrong instrument, further prevention was made with the assistance of visual identification, and handles were made with four different colours and shapes with no two adjoining sections having the same colour to prevent the fault. (Durmus 2015). The method was used by the signalmen in two ends A and B for safety procedures of line clear command allowing the train to pass. Before dispatching the train, the signalman, A provides all the criteria of Line Clear to signalman B. the galvanometer was used to dispatch tokens in order to give a clear idea to the signalman that the train is ready to proceed. Electronic token block has been now replaced with a more advanced feature called a radio-electronic token block. For the safety procedure of passing trains, the electronic token block is used for passing trains without the complication of the wrong signal as signallers have the opportunity to know what is the correct time of the train to pass by communicating with each other from both ends through tokens. After the arrival of the train at signalman B, the key token is obtained from the driver after replacing of signals and checking of the train is complete. (Katsuta et al. 2020). This system has helped to lead the development of the electronic system in railway operation as the train can run over consecutive single-track sections. The system it was introduced to prevent danger as only one token has been issued to the driver at one time. The configurations of the tokens were different belonging to different adjacent sections in order to prevent inserting the token into the wrong instrument. This system was mainly developed in order to remove the inflexibility of the busy lines. The electronic token block stated the main electronic era of signalling trains safely from both ends and technology is improving and new technologies are being taken into consideration for preventing danger and safety of the passengers. (Katsuta 2015).
Radio Electronic Token Block called RETB is a system of blocks used for railway signalling designed for signalling single-track rail routes with medium and light traffic density. RETB is a cost-effective in-cab system of signalling used by railways in single track and rural railway networks. The main feature of RETB is its innovative radio networks of architecture that increases safety and efficiency. The Comms design of RETB comes with its radio network. This helps in signalling the train from one station to another without hesitation. The RETB from its base stations has various self-contained chains of networks where radio calls from trains are transferred from the base station to other base stations and the signal is back to the main base centre. (Booth 2012). The train radios automatically tune themselves to the strongest radio channel as they travel along the route. The users due RETB hears all calls and help in enhancing situational safety and awareness. RETB works in a unique way, when a train is required to move to a new section the signaller issues authority permission of movement token from that section to the train. In order to capture that token, the driver activates the receive function from the train using in-cab equipment. This enables a series of radio transmissions that are coded in such a way that matches the identification number of the train. With these safety standards, the train driver guarantees that they have received the correct token. (Buksh et al. 2018). After the token has been collected by the driver the train proceeds into the track block by deactivating the automatic protection block of the train at that section. The interlocking system of grade SIL 4 controls the issue of all movements of tokens and also protects the section of the single track. The RETB has a signalling desk that provides simple centralized control of the entire route. It can control a route of 500km but if the route increases the splitting of areas of RETB into multiple desks helps in sharing the workload by providing information. (Xie et al. 2014). RETB also has the remote condition of monitoring built-in system. Remote users and signallers can receive live data from base stations and mobile radios and the radio network also provide the historical trend data which ultimately helps the technicians in diagnosing the issues early in order to prevent danger. RETB has fully supporting crews of line staff and depot teams with the necessary equipment in providing quick support. RETB has a flexible on-train equipment installation and is already in use by stock types as well as 23 locos. (Lopez, Aguado & Jacob 2014).
Radio Electronic Token Block (RETB) and its Features
The Tokenless block has been a few systems used in the early days of railways which were introduced for single lines and were formed by the British railways. The Tokenless block instrument consists of a single needle indicator with positions counted as 3 and those are Normal, Train In section, and Train Accepted. The basic feature of the Tokenless block was in passing trains and in order to communicate with signallers. (Vignesh et al. 2014). If signalman A at the box wishes to send a train to colleague signalman B at other ends, then A pushes the offer and in return, signalman b accept the offer and this will turn both side of the train line accepted and the lock will get released at another end. When the train reaches the section and passes beyond the home signal, the train will operate, and block indicators will turn to Train in Section. If the train completes the two-track succession the indicator will change to Train Arrived and it will get registered in the system. After signalman B sees the train arriving, he returns the button to Normal acceptance and the train arrived button is pressed. After the completion of the arrival of the train both the indicators return to normal and the block is clear. The advantage of the blocking system was in the ease of switching-out facilities and can be provided at the passing loops. On one loop reversible signalling is provided and a locking frame containing a switch-lever helps in determining the sections are clear or not. (HIRAGURI et al. 2012). This function of operation was used by early railways for providing drivers and signallers an option to prevent danger by controlling sections and acceptance. This system was mainly used in single-line railways and tokens were not used in this method. This signalling was designed in such a way that the controlling signal will only allow only one train at a time and only one train to enter the given line. The signaller at the other end of the track was used to visually check the whole movement of the train and confirmed that the train has left the section and confirmation was done by using the tail lamp. This signalling further changed because of the inflexibility of signallers confirming movement in certain conditions.
Booth, P.D., 2012, May. Intermittent and continuous automatic train protection. In IET Professional Development Course on Railway Signalling and Control Systems (RSCS 2012) (pp. 89-117). IET. DOI: 10.1049/ic.2012.0046.
Buksh, A., Sharples, S., Wilson, J.R., Morrisroe, G. & Ryan, B., 2018, February. TRAIN AUTOMATION AND CONTROL TECHNOLOGY–ERTMS FROM USERS’PERSPECTIVES. In Contemporary Ergonomics and Human Factors 2013: Proceedings of the international conference on Ergonomics & Human Factors 2013, Cambridge, UK, 15-18 April 2013 (p. 168). Taylor & Francis. https://dx.doi.org/10.1201/b13826-40
Durmus, M.S., 2015. Control and fault diagnosis of railway signaling systems: A discrete event systems approach. DOI :10.18910/52189
HIRAGURI, S., FUKUDA, M., FUJITA, H. & ONO, Y., 2012. Train control system for secondary lines using radio communications in specific area. Quarterly Report of RTRI, 53(1), pp.1-6. https://doi.org/10.2219/rtriqr.53.1
Katsuta, K., 2015. Cost effective railway signalling by wireless communication among onboard controllers and switch controllers. IET intelligent transport systems, 9(1), pp.67-74. https://doi.org/10.1049/iet-its.2013.0169
Katsuta, K., Maki, K., Ogata, T., Hasejima, N., Sakayori, G. & Takahashi, J., 2020. Traffic Flow Control Method at Intersection by Electronic Token. Transactions of Society of Automotive Engineers of Japan, 51(5). https://doi.org/10.11351/jsaeronbun.51.836
Lopez, I., Aguado, M. & Jacob, E., 2014. End-to-end multipath technology: Enhancing availability and reliability in next-generation packet-switched train signaling systems. ieee vehicular technology magazine, 9(1), pp.28-35. https://doi.org/10.1109/MVT.2013.2295072
Vignesh, M.K.S.M.D., Sanjay, M.V., Umasankar, M.N.H.M.L. & Student, U.G., 2014. REALIZATION AND FORESTALLING OF FLAWS AND RUINING IN RAILWAY NETWORK BY MCEC. Doi:01.0401/ijaict.2014.04.07
Xie, G., Hei, X., Mochizuki, H., Takahashi, S. & Nakamura, H., 2014. Safety and reliability estimation of automatic train protection and block system. Quality and Reliability Engineering International, 30(4), pp.463-472. https://doi.org/10.1002/qre.1498
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