1MC on submarine

I know that the “1MC” is a public-address system for making announcements within a submarine. However, for what is “1MC” an acronym? Also, am I correct that the two-way internal communications system within a submarine is the “7MC?” (I saw that on someone’s web site.) For what is “7MC” an acronym? Why not “2MC,” since it’s a two-way communications path?


Sorry you didn’t get an answer on this SteveAtlanta, so I’ll take a shot. The 1MC stands for “General Announcing System (Navy Shipboard)”. On a boat, there’s only two locations, the control room and the nuclear control panel aft. I can’t remember the specific circuits but they all have meaning. I know that the 5MC on a carrier is designated for announcements on the flight deck (no 5MC on a boat) (my office mate served on a flattop). The 7MC was used for communications between control, sonar and the torpedo room on the boat.


Oops, now that I’ve thought about it more, I was incorrect (called a sonar buddy to check…). The 27MC was used for comms between control, sonar and the torpedo room. The 7MC was used for comms between control and engineering.

The Navy uses a series of numbered circuits to standardize different communication channels within a ship. (MC might stand for messenger circuit or it might have simply been the next 2-letter code that was available when they decided to go around labeling things. I have not been able to discover the answer to that.) As BF noted, each specific channel or circuit gets the same numeric label on all ships simply to standardize terminology from one ship to the next when discussing the circuits.

This Navy document (.pdf format) discusses the circuits beginning at the bottom of page 4-13.
This is the Google cached html version.

MC stands for “Microphone Control”.

--IC3 Stentor, your friendly neighborhood 1MC technician.

To close the loop on the “2MC” mentioned in the OP, that is the designation for the one-way announcing system that sounds only in the engineering spaces.

During drills, I used the 2MC extensively. It was the fastest way to get orders/info to personnel out in the engine rooom.

With respect to the “7MC” (Submarine control), it was used when the Officer-of-the-Deck (OOD) was on the bridge (at the top of the sail) during surfaced ops. A temporary “bridge box” was installed with some rudimentary instruments, along with a microphone that could sound on the 1MC circuit (for the whole ship), or the 7MC circuit (for comms to the control room below). I don’t believe it was used to communicate with Maneuvering/engineering.

–robby (ex-Submarine officer)