British Railway Signals - Track Circuits, Warning Systems and

India's train crash shows chronic lack of investment in improving safety, experts say

Malden DSME Ltd - Ground Level Signalling - track circuits technical details

BR AUTOMATIC WARNING SYSTEM

Signalling, The Railway Technical Website

Frequently Asked Questions - Empire State Passenger Association

Signalling, The Railway Technical Website

British Railway Signals - Mechanical and Fog signals

Rail Field Equipment

A long engagement – railways, data and the information age - Science Museum Group Journal

Early Railway Signals

Evolution and beyond Railway Signals and Blocks