Axle Counter System

Overview

An axle counter system detects the presence of a train within a track section by counting axle passages at the section entrance and exit. When entry and exit counts are unequal, the system asserts "train in section" to the signalling system, preventing other trains from entering the same track block.

How it works

Two sensors are installed below the rail foot at each block boundary, one per rail. Each sensor is an inductive pickup coil tuned to the frequency at which a passing wheel generates eddy currents in the rail. When a wheel passes, the magnetic field changes, inducing a pulse in the coil.

The Axle Counter Evaluation Unit is a dual-channel safety processor receiving pulse streams. It counts each pulse and maintains the running count for the section. When entry count > exit count, the safety relay output energises, signalling the interlocking system.

Each Axle Detection Sensor is wired back to a junction box at the lineside, which houses surge protection and signal terminals.