scope:

This standard applies to London Underground maintained equipment only.

This standard applies to 10kHz overlay rail circuits, and to de-energised rail circuits using blockjoints. It does not apply to mechanical treadles or to electromagnetic position detectors.

This standard is primarily intended for use by the Asset Steward.

This updated standard replaces E7154 A2 and TLL-ENG-S7253-A1, which are withdrawn.

Note: The functions and performance criteria for track circuit based train detection systems are detailed in S2505 (Train detection systems), and their maintenance requirements are specified in S2541 (Maintenance of track circuits).

Purpose

This standard defines the minimum maintenance requirements for rail circuits and associated equipment used on London Underground.

Rail circuits are safety critical assets, typically used to enable the safe clearing of signals or the safe releasing of routes.