somersault signal

plural somersault signals

1. rail transportA semaphore railway signal that is pivoted in the centre of its arm.

   1 more example

   Realising their shortcomings, BR stripped out most of the smaller wayside stations between Peterborough and Grimsby on September 11 1961, although not those on the branches because there would have been nothing left to sustain them. Those that survived were working museums right to the end, with somersault signals and original interior fittings and signage.

   2020 November 18, Howard Johnston, “The missing 'Lincs' and the sole survivor”, in Rail, pages 58–59