Signal Track Circuits Configuration Guide

Table of contents
  1. Signal Track Circuits Configuration Guide
    1. Introduction
      1. Track Circuit Link Event ID
      2. Using Track Circuits

Introduction

When configuring signals and their corresponding Track Circuits within a signaling system, you are establishing a relationship between the track circuits and the signals, specifically with respect to the signaling aspects and the speeds they represent.

The following outlines the steps:

  1. Configure All Masts: Initially, set up all signal masts with their respective configurations. Note that the “Track Circuit Link Event ID” is used later when configuring the Track Circuits.
  2. Link Track Circuits to Masts: Begin with the mast located furthest downstream and proceed upstream. For each track circuit, copy from the corresponding mast configuration the “Track Circuit Link Event ID” into the track circuit’s configuration field. This action establishes a direct link between each mast and its associated track circuit.
  3. Utilize Logics and Conditionals: After linking, use logics and conditionals to interpret the speeds indicated by downstream track circuits (e.g., 0 for Stop, 1 for Restricting, etc.). These interpretations guide the setting of aspects on masts based on the conditions signaled by downstream track circuit speeds set by a remote (downstream) mast. For example, if a downstream track circuit indicates a speed of 0, the upstream mast should display a ‘Stop’ aspect.

Since the Track Circuit to Mast linkage is performed using an LCC Event ID, the mast can be defined and managed from different LCC Node.

Below is a summary of the Track Circuits Configuration CDI fields (shown in the dialog on the right):

  • Track Circuit (tab): There are tabs for each circuit, allowing individual configuration for each track circuit.
  • Description: A field to optionally enter descriptive information about the track circuit or mast.
  • Track Circuit Link Event ID: This is a crucial field where you enter the Event ID that corresponds to the ‘Track Circuit Link Event ID’ of a downstream mast. This ID ensures that the aspect shown by the downstream mast influences the track circuit in question.

The Track Circuit Link Event ID establishes a connection between a signal mast and a track circuit. The track circuit functions as a variable that can be referenced when defining signal conditional statements. When a downstream mast is associated with a track circuit via this link, the variable is automatically updated with the track conditions (e.g., occupancy or speed) governed by the downstream mast. This track circuit variable can then be used when configuring an upstream mast to set its aspects based on downstream conditions.

flowchart LR
MastB["Mast B"];
TrackCircuit["Track Circuit <br/>(variable)"];
MastA["Mast A <br/>(upstream)"];

subgraph layout ["Train Layout"];
direction RL;
subgraph block ["Track Block (downstream)"];
TrackCircuit <.-> |"Linked"|MastB;
MastB -->|"Track Speed <br/>(realtime updates)"| TrackCircuit;
end
TrackCircuit <.-> |"Linked"|MastA;
MastA -->|"Track Speed <br/>(realtime checks)"| TrackCircuit;
end
classDef lSalmonStyle fill:#FFA07A,stroke:#333,stroke-width:2px,font-size:16px;
class TrackCircuit lSalmonStyle;
classDef lBlueStyle fill:#ADD8E6,stroke:#333,stroke-width:2px,font-size:16px;
class M1,M2 lBlueStyle;
classDef lightGrayStyle fill:#d3d3d3,stroke:#333,stroke-width:2px,font-size:16px;
class layout lightGrayStyle;

This diagram illustrates the relationship between a Track Circuit, downstream mast (Mast B), and upstream mast (Mast A) in a signaling system:

  1. Track Circuit as a Variable:
    • The Track Circuit is treated as a variable that reflects the conditions of the block, such as Track Speed or occupancy status.
  2. Downstream Mast Association:
    • Mast B (Downstream Mast) is linked to the Track Circuit through the Track Circuit Link ID, which ensures that Mast B’s configuration and status are connected to the Track Circuit.
  3. Upstream Mast Influence:
    • The Track Circuit provides Track Speed and other conditions to the Upstream Mast (Mast A), allowing Mast A to set its aspects based on the downstream block conditions.

This system ensures coordinated signaling by using the Track Circuit as a shared variable for both downstream and upstream masts.

Using Track Circuits

“When configuring the interaction between two signal masts—A (upstream) and B (downstream)—it’s important to establish a clear communication pathway for track conditions that influence signal operations. This is achieved through the ‘Track Circuit Link Event ID’. This unique identifier links Mast B to a specific track circuit, which monitors and reports the speed of a section of track. The reported speed from this track circuit is then utilized to determine and set the appropriate aspect at Mast A. This setup ensures that the aspect displayed by Mast A is directly informed by the real-time conditions of the track as detected by the circuit linked to Mast B, enabling accurate and safe signaling based on current track usage and conditions.”

Using Mast A and Mast B previously mentioned, let’s see how the track circuit is implemented:

  1. Rules to Aspect Configuration for Mast B:
    • For Mast B, determine the aspects (e.g., Stop, Proceed, Caution) that it will display under various conditions.
    • Each aspect configured is associated with a unique “Event ID”. This “Event ID” serves as a digital signature for the specific aspect and condition it represents.
  2. Linking a Mast to a Track Circuit:
    • From Mast B’s “Rules to Aspect Configuration”, take note of the “Track Circuit Link Event ID” and copy it to a track circuit configuration.
    • This configuration step using the “Track Circuit Link Event ID” creates a direct link between the track circuit and Mast B.
  3. Logics and Conditionals Configuration:
    • When configuring the Logic for setting the aspect of Mast A, configure a Condition to test the speed of the track circuit. For example, if the track circuit is reporting an Approach speed for the downstream mast, then aspect for Mast A should be set to Stop.
  4. Operational Outcome:
    • Now, when Mast B displays an aspect (signaled by the activation of the corresponding Event ID), the Logics and Conditionals configuration for Mast A’s can detect the changes in the track circuit’s reported speed and change the aspects for Mast A.
    • This ensures that the signaling along the track reflects a consistent and logical flow of information, enhancing both safety and efficiency.

This linkage technique ensures that signals are not only aware of local track conditions but also communicate with each other to maintain a coherent and safe flow of rail traffic, particularly in configurations where the decision made at one signal mast (B) directly influences the operational state of another mast (A) upstream.

Last updated on: May 10, 2025 © 2025 Pat Fleming