This junction is west of Edinburgh. This is where the Edinburgh and Glasgow Railway of 1842 is met by the Forth Bridge Connecting Lines (North British Railway) of 1890. The location is just east of the former Saughton station. Both lines are double track and from the east of the junction to Edinburgh the line is quadrupled.
When first opened the line east was double track. It was rebuilt and an additional two tracks opened in 1895 for which the signal box here was replaced in 1894. The box was on the north side of the junction, the original box was on the south.
The location was renamed from Corstorphine to Saughton in 1902 (the opening of the Corstorphine [2nd] branch.
In 1908 the signal box took over Saughton East Signal Box and in 1910 it took over Saughton North Signal Box and Saughton West Signal Box.
The box closed in 1975, taken over by the new panel box at Haymarket Power Box.