A history of railway signalling: From the bobby to the balise

The paper outlines the history of signalling from opening of the first purpose-built passenger-carrying railway in 1830 with hand signals, through the developments of fixed lineside signals, electric telegraphs and interlocking mechanisms for points and signals. From the appearance of power signalling at the turn of the 20^th century, it follows the development of first electrical and then electronic signalling technology through to present day communication-based systems.