This was a short-lived system for conveying information quickly over large distances, as described by the Telegraph Operator in Act 3, Scene 5 of the opera. It used a series of hilltop telegraph stations with large semaphore arms which could be manipulated to convey a series of symbols. It was in use in France and other European countries, including Britain, for a period of some fifty years during the late eighteenth and early nineteenth centuries, until it was superseded by the electric telegraph. In the opera, Monte Cristo bribes the Telegraph Operator to send a false signal which precipitates a financial crash and bankrupts Danglars.

A replica of a French semaphore tower in Nalbach, Germany.