Introduction

This page provides a Register of all the known electrical Track Circuits on the former Somerset & Dorset Joint Railway (S&DJR).

It is not known if any official records survive which list all the S&DJR track-circuits (TCs). The information contained in this Register has been compiled by studying surviving copies of S&DJR signal-box diagrams, upon which usually any TCs were marked, and other railway documents. It is possible therefore that there may have been some TCs which were added not long before closure of the line in 1966, but for which updated signal-box diagrams do not exist to reveal their presence.

In the absence of any definitive records it is not possible to be certain exactly when the S&DJR started to install any TCs, but it is probable that the first example was at Midford, where one is known to have been in use by late-1923. There was not a large number of TCs on the S&DJR and indeed almost a third of them existed at only one signal-box, Templecombe No 2 Junction, after it took over the work of Templecombe No 3 Junction in 1933. Almost all the other signal-boxes with TCs had merely one or two each. Several of the TCs were added during the British Railways (BR) era as a result of maintenance work on facing points, when the mechanical locking-bar component of the Facing Point Lock (FPL) mechanism was replaced by a TC through the points which controlled an electric lock on the FPL lever (and usually also a lock of the relevant point lever).

TCs were identified simply by letters, a separate sequence 'A' 'B' 'C'... etc being used at each signal-box. There were exceptions at Evercreech New, where there were four short TCs (two on each line) provided for the purpose of operating a warning bell at a foot-crossing; these TCs apparently had no signalling function and did not appear on the signal-box diagram, so it is not known how they were identified. It should be noted that at some locations which had both track-circuits and treadles a single sequence was used for both types of equipment, whereas at other locations separate sequences were used for the different types. In BR days there is some evidence of the use of BR (Western Region) identification terminology.

The status of a TC - 'clear' or 'occupied' - was indicated in the relevant signal-box by means of an electric indicator mounted on the instrument shelf above the lever-frame. Only in one signal-box (Templecombe No 2 Junction) was the practice adopted of providing an 'illuminated' signal-box diagram (which incorporated lights to show the TC status in the relevant parts of the tracks marked on the diagram) and this was not provided until about 1951/52 to replace the existing indicators.

Track-Circuit indicators in Templecombe No 2 Junction signal-box circa-1950

Track-Circuit Register

The Track-Circuit Register entries are listed in the line order of the various relevant signal-boxes, but an alphabetical Index to Locations is provided also for quick access to individual signal-boxes.

The following explanations of Track-Circuit Register entries should be noted:-

• The 'Location' is the signal-box controlling the length of track equipped with the TC.
• The 'ID' is the identification letter of the TC at that location.
• The 'Date' is the date of installation of the TC (where known). Any dates prefixed 'post-' are merely the earliest known date and not necessarily the actual year of change. Unless stated otherwise, all TCs are believed to have remained in use until their respective signal-boxes were closed.
• The 'Remarks' describe the position and extent of the TC etc.

© CJL Osment 2013-21
TC indicators photograph courtesy Ian Matthews