Flawless Communications for Cab Signaling System


Our world-renowned railway client had been using their in-house cab signaling system for almost 20 years, which gradually became obsolete. In particular, the communication technology that was used became outdated. This created both safety and cost risks, and couldn’t provide compliance with modern PTC standards and FRA requirements.


Client Challenge

Ensure reliable and PTC-compliant cab signaling communications for instant crew notifications on speed restrictions and automatic train stop.

Project Objective

Advance the communication technology for a cab signaling system to ensure rapid and error-free message delivery.


To provide seamless data transfer on speed restrictions, we modernized the communication service for the cab signaling system by basing it on TCP – one of the most widely adopted protocols, which provides ordered and error-checked data delivery over IP networks. 

The PSA team modernized each unit involved in cab-PTC communications to receive and transmit cab signaling messages via TCP protocol. We modified message definition by including TCP transfer and performed WIU (Wayside Interface Unit)-related upgrades to transfer new type of messages:

  • Changes to WIU application builder to execute wayside operations by TCP-delivered command

  • WIU web interface updates, including  web pages, schemas, and parameters handling updates for remote control

  • CPU firmware adjustments, including vital code, for flawless WIU communications

The delivered advanced messaging service supports the ability for the client’s cab signaling product to communicate over the reliable and error-free TCP protocol for the train crews to be instantly informed on speed restrictions, and for penalty train stop if overspeeding. The upgraded cab signaling system fully meets the definition of a PTC system.

To explore more technical details click here.

Development Included

  • Requirement clarification
  • Software updates
  • Firmware updates
  • Testing & Bug fixing



  • An enhanced messaging service for cab signaling

  • Full compliance with PTC & FRA requirements

Technology Breakdown

Project size
  • 2 Software Engineers
  • 2 QA Engineers
  • 4 months

Further Cooperation

For this client, PSA team performed high volume of projects related to connectivity for safety-critical railway equipment, such as Wayside - CTC Communication Service and High Availability fro Mission-Critical Connection.

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