St. Erth is situated a few miles from Penzance, where the branch to St. Ives leaves the main line.
The dog chart is marked 23 October 1941 and the layout at that time is shown on a box diagram generated from a 1964 office copy and the scheme plan and locking sketch for the alterations in 1964. A locking table has been derived from this dog chart and shows the mechanical locking at this time.
In April 1958, FPL bars on 44 and 53 were removed and track circuits installed. An amended dog chart (to be uploaded soon) is dated 11 July 1964 and shows sequential locking being installed and each-way locking on 44 and 53 having been removed. A later box diagram has been reproduced from an office copy held by Kidderminster Railway Museum and shows the layout at the end of 1964. During 1964 the following work had been undertaken:
The later box diagram therefore shows the position once this work had been completed.