Standard

Audio Frequency Track Circuit Inspection and Maintenance

Abstract

This standard offers requirements necessary to ensure the safety and reliability of audio frequency track circuit systems.

Document History
Document Number Version Publication Date Publication Related Information
APTA RT-SC-S-009-03 Rev. 2 01/31/2025 Published Current
APTA RT-SC-S-009-03 Rev. 1 12/31/2014 Published Superseded

Keywords

AF track circuit, audio frequency track circuit, bond, HF track circuit, impedance bond, shunt, shunting device, signal, track circuit

Summary

This standard provides audio frequency track circuit tests that verify train detection (shunting), and continued proper operation. These tests include recording the measured values for comparison over time to reveal trends in transmit and receive signal levels, which can help predict possible equipment and/or track deterioration. This standard also provides track circuit inspection requirements.

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