On the conning platform, an instrument called the engine order telegraph (fig. 2-8) communicates speed orders  to  the  engineroom.

The  engine  order  telegraph  is circular, with duplicate dials divided into sectors for flank, full, standard, 2/3, and 1/3 speed ahead; 1/3, 2/3, and full speed back. A hand lever fitted with an indicator travels over the circumference of the circular face of the instrument.

When the handle is moved to the required speed sector, the engineroom complies with the order immediately  and  notifies  the  bridge  by  operating  an answering pointer that follows into the same sector.

A ship with one engine has a telegraph with a single handle. Two-engine ships usually have a handle on the port side and another on the starboard side of the telegraph,  controlling  the  engines  on  the corresponding sides. Be sure you have grasped the handle for the correct engine before you operate it.

If the answering pointer moves to the wrong sector, does not move at all, or moves to a line between two sectors so that you are in doubt about the speed set on the engine, repeat your operation on the lever. If the pointer does not move, report the situation immediately to the officer of the deck.

If a casualty occurs in the engineroom, the speed may be changed by the engineroom without orders from the officer of the deck. In such an event, the answering pointer moves to the speed set in the engineroom. Report any change in the engine order telegraph to the officer of the deck at once. Also report to the OOD immediately if you fail to receive an answer on the pointer when you indicate a speed. The safety of your own ship and others may depend on the immediate and correct transmission of orders to the engines.

Before  getting  underway,  the  telegraph  is  always tested  by  moving  the  handle  to  each  sector,  and checking the response on the answering pointer. In the event of casualty to the telegraph, the engineroom receives orders over the sound-powered phones.

Engine Order Telegraph

Explanation From: Integrated Publishing Web Site - Courtesy of antiquesofthesea.com