Interior communications electricians install, maintain and repair the equipment needed for interior communications within ships and shore facilities. These communication systems include public address systems, interior telephone systems, alarm systems, engine telegraphs to communicate orders for changes in engine speed from the bridge (ship's command station) to the engine room, certain kinds of ship control and equipment monitoring devices, the ship's gyrocompass, the rudder position indicator, audio-visual equipment for the ship's TV entertainment systems, advanced navigation and various other equipment.