From Allbrook signal box, just north of Eastleigh in Hampshire. The track from Allbrook box to Shawford station was double until 15th March 1931, when the up and down relief lines were laid. The down relief line was extended from Shawford station to the junction in 1943.

The plunger would have been used for accepting trains from the Didcot and Newbury line and other down local line trains, as well as for sending bell signals to Shawford Junction box for up local line traffic.