A ship's telegraph is also known as an Engine Order Telegraph and is a way of communicating instructions between the wheelhouse of a ship and the engine room.
The Engine Order Telegraph has at least two parts, each with a round dial showing engine instructions such as Full Ahead, Slow Ahead, Stop, Show Astern etc. A handle is turned on the ship's telegraph and the new position with its corresponding instruction is related to the other end of the telegraph.
The system was pioneered in the 1870s by a Liverpool company called Chadburns so many people refer to the telegraph as a Chadburn Telegraph or, simply, a Chadburn.
These fascinating devices, often with brass pedestals and surrounds, are increasingly a sought after item for people wanting to bring a nautical touch to their interior design.