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PACs in a Railway Signaling Application

PACTECH / ICP DAS (E17W35_06, by Cony Yu)

A Railway Signaling System is a series of chain control systems where additional back-end devices may also fail if one device fails. This can cause difficulties for maintenance personnel when trouble-shooting, as they are typically only able to check each device individually to determine which operation has failed based on the final failure result. This means that the maintenance personnel can be easily confused as it might be difficult to locate the source of the problem.


A signal can be effectively operated by using a railway signaling monitoring and control system and the management can be centralized. This makes it easily to analyze and monitor the causes of failure, quickly ruling out or tracing the source of any problems so that any device failure can be detected in real time. In this way, the safety of the railway operations will be enhanced, train punctuality will be improved and it will be easier to achieve any maintenance work, thereby creating a reliable and efficient railway signaling management system.

As the number of high-speed trains increases together with the frequency of train services, external factors such as the climate and the risks surrounding night time driving, etc., railway signaling systems have become progressively more important. The purpose of a railway signaling monitoring and control system is aimed at improving the reliability and efficiency of the railway signaling operations.

By using network transmission and user-friendly graphic control interfaces, it is easy to perform the operations related to the hardware or software devices involved in railway signaling management. The information can then be collected for further data analysis. Furthermore, the system makes it easy to quickly identify or trace the source of any problem so that any device failure can be detected in real time.

System Architecture

The railway signaling monitoring and control system includes three parts: a signal converter, SCADA systems, and a signal processing and control unit. In this case, ICP DAS provides the WinPAC-8000 series of programmable automation controllers (PACs) as the solution for signal processing and control.

System Architecture

Signal Processing and Control unit

A WinPAC-8000 series PAC is used for signal processing and control. It features a high performance CPU, large-capacity memory and storage space, a wide range of input/output interfaces, such as USB, VGA, Ethernet, RS-232 , and RS-485, etc., and a built-in real-time operating system and firmware that meet the IEC-61131-3 standard. The PAC also provides multiple programming options, such as a functional block diagram (FBD), a ladder diagram (LAD), a Sequential Function Chart (SFC), and Structured Text (STL), etc.

The PAC is able to send or receive messages with the help of digital or analog plug-in modules, such as the I-8014W, I-87053W or I-87057W, or via the RS-485/RS-232 interfaces, such as the I-8144iW.

Once the data is processed, the PAC can perform data exchange with the SCADA system, the traffic control center or the central server via the Internet. The sent/received messages include AF track circuit information (communication), PF track circuit information (communication), the status of the emergency stop button(digital), any switch information (digital, analog), the route setting information (communication), transport direction information (communication, digital), information from the train stopping module (analog), the ground detection status (digital), power supply information (digital, analog), temperature and humidity information (communication), access control status (digital), and signal converter data (communication) etc.

Main Specifications of WinPAC-8000 series

Signal Converter

By using an ICP DAS WinPAC-8000 series controller, the signal converter can be connected to a Vital Processor Interlocking (VPI), a Non-Vital Processor Interlocking (NVPI), and Visual Display Unit (VDU) modules via an RS-422/RS-232 interface to send, receive and exchange information with the SCADA system, traffic control center, or the central server. The information either sent or received includes Centralized Traffic Control (CTC) information, VDU information, Passenger Information Display System (PIDS) information, and communication information between train stations, etc.


To implement a track signal monitoring and control system, the system integrator who plans and builds the system usually needs to invest a large amount of money in the initial outlay, and the cost for mid- and long-term maintenance is also quite imposing. In recent years, with hard-work combined with its cooperative system integrator, ICP DAS has accumulated a broad range of experience in this field. We believe that further cost-effective applications for track signal systems will be developed in the near future.

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ICP DAS was established in 1993 and strongly focuses on innovation and the enhancement of industrial automation technology. ICP DAS continuously endeavors to develop a comprehensive selection of products ranging from remote I/O controllers, distributed I/O modules, I/O data acquisition boards, programmable automation controllers, industrial communication modules, web-related products, motion control systems, SCADA/HMI software to automation solutions for applications critical to energy management, motion automation, smart factories, intelligent buildings, and smart cities. Our ambition is to provide a wide range of high-quality products and versatile applications, together with prompt and efficient services, that can be implemented to assist in the continued success of our clients worldwide.

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    • Thank you for your comment. We are glad that you enjoyed on our blog.
      We will continuously share more ICP DAS successful experiences and Smart Transportation solutions to help development and enhancement.

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