Semaphore station. Historical artwork of a semaphore station in Algeria. Semaphore is a system of communication based on visual signals. The station has a pair of wooden arms on its roof. These could form 196 different arrangements, each representing a letter, number, or other meaning. Messages were passed from one station to another by operators in the stations, who duplicated the signals they observed from the station preceding them in the line. The last operational semaphore station closed in 1860 in Algeria. Published in La Telegraphie Historique (History of Telegraphy) by Alexis Belloc in 1888.