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In the 1960s the Shrewsbury & Hereford line came under the control of the London Midland Region (LMR) of British Railways as far south as Craven Arms, meaning the GWR design box and frame underwent some notable changes. It now has standard BR bakelite block instruments, a LMR style block shelf - which bears LMR style lamp and arm indicators and the modern diagram - and electric lock releases actuated by catch handles on most electrically locked levers, rather than the GWR/BR(W) style block shelf plunger.
The layout of the junction has been extensively remodelled since the late 1960s/70s which has caused many levers to be taken out of or change use. This means for example that lever 5, which was originally the inner home signal reading off the Severn Valley line, is now the Up starting signal and therefore in continuous use.
==Signalling diagram==
As part of the significant redesign of the layout at Sutton Bridge, many of the original GWR/BR(W) design signals were replaced with standard BR(LMR) upper quadrant signals, unusually resulting in a GWR box controlling LMS style signals. The Up inner home on the Cambrian branch and the Down home bracket remain GWR/BR(W) lower quadrant design however. On the latter, the space can be made out that originally controlled the junction onto the Severn Valley line. The box also controls colour light signals in the form of its Up distant signals on both the Hereford and Cambrian lines, and the Up home on the Hereford line is a 3-position colour light, which only shows green when the Up inner home and starting signals are cleared. It will show a yellow when reversed, only once the home berth track circuit immediately in rear of it has occupied, effectively checking the train down to a low speed in accordance with what was (and still is on the SVR) Rule 39(a).
The box works to Absolute Block regulations to the north and south, working to Severn Bridge Junction to the north and Dorrington to the south (and Marshbrook when Dorrington is switched out). It works to Machynlleth Signalling Centre under Track Circuit Block regulations as far as the commencement of Cab signalling board on the Cambrian, beyond which the in-cab signalling system European Rail Traffic Management System (ERTMS) comes into effect. Controls on communication between Sutton Bridge and Machynlleth are mounted on the diagram. Unusually for a box of its size, Sutton Bridge Junction has the capacity to switch out and does so on a daily basis. Originally the box worked by Absolute Block to the now closed Coleham and Bayston Hill boxes to the north and south respectively, to Hookagate signal box towards Machynlleth, and to Burnt Mill Junction box on the Severn Valley Line. However, this box closed in 1937 and communication was then by Electric Train Token to Berrington signal box.
==See Also==
* [[List of signal boxes]]
