SHUOZHOU, Sept. 20, 2019 (Xinhua) -- Flag semaphore, an ancient information-conveying system widely used in the maritime world, is also adopted in railway operation.

Despite the progress of modern technology, flag semaphore still plays an important role in ensuring the safety of trains, due to complex working environment.

A railway worker in Shanxi, north China, presents examples of flag semaphore in railway system, with LEGO bricks.