semaphore signal

noun2

1. •
   Any signal sent by semaphore.
2. •
   A railway signal with a moving arm mounted on a signal post or gantry, the position of the arm indicating whether a train should stop or proceed; they are now largely replaced by colour light signals.

   • The phased programme will run from 1 to 23 February, with semaphore signals replaced with modern colour lights. — 2019