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GWR Route: Banbury to Wolverhampton

GWR Route: North Warwickshire Line

Birmingham Snow Hill Station: gwrbsh1742

Electrically powered mechanisms for operating semaphore signals were more complex when they were interlocked with route indicators

Electrically powered mechanisms for operating semaphore signals were more complex when they were interlocked with route indicators. This is a close-up of the mechanical linkages and electrical contacts on the signal post at the south end of platform No 7. The main up platform line Starting Signal was a standard four foot long, lower quadrant semaphore signal at the top of this post, but it is just out of sight in this photograph. It was controlled by lever 4 in the Birmingham South Signal Box. This lower signal was what is termed a ‘Draw Ahead or Shunting’ signal and was distinguished by its lower position on the signal post and by having a shorter semaphore arm (three foot long). It was provided to regulate the passage of trains without authorising them to pass any Stop Signals which were set to Danger, this could be used to either:
      a) direct a train or locomotive into a siding
      b) authorise a driver to pass the Starting Signal for shunting purposes only
      c) instruct a train to be drawn forward closer to the Stop Signal. This final instruction option was not introduced                 until after 1923, but it was a regular requirement at Snow Hill, where the long platforms were designed to                 accommodate two trains - one before and one after, the centrally positioned scissor switches.

This semaphore signal at Snow Hill was interlocked with the route indicator above it and when the signal was operated to clear, this would illuminate the required instruction as follows:
      Engine Spur – lever 30 from Birmingham South Signal Box
      Shunt – lever 5 from Birmingham South Signal Box

The engine spur was a short siding located adjacent to the up line at the tunnel entrance.

Robert Ferris

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