Signal box

History

Originally, all signaling was done by mechanical means. Points and signals were operated locally from individual levers or handles, requiring the signalman to walk between the various pieces of equipment to set them in the required position for each train that passed. Before long, it was realized that control should be concentrated into one building, which came to be known as a signal box. The signal box provided a dry, climate-controlled space for the complex interlocking mechanics and also the signalman. The raised design of most signal boxes (which gave rise to the term tower in North America) also provided the signalman with a good view of the railway under his control. The first use of a signal box was by the London & Croydon Railway, in 1843, to control the junction to Bricklayers Arms in London.