1 Main Circuit

This provides a means of transmitting general information and orders to all internal ship spaces and topside areas, and is loud enough that all embarked personnel are (normally) able to hear it.

It is used to put out general information to the ship's crew on a regular basis each day.

The system consists of an amplifier-oscillator group which is located in the IC/gyro room, a microphone control station, portable microphones at each control station and loudspeakers located throughout the ship.

[1] During an incident involving a casualty, the 1MC is a communication tool used by DCAs (damage control assistants) to keep ship members alerted and informed of casualty location area, status, and incident response efforts by the DC organization.

[1] The 1MC is also used for transmitting various alarm sounds to alert the crew of specific impending dangers such as an inbound anti-ship missile, chemical attack, collision, or a flight deck crash.