Jeffrey LewisCommunicating with SSBNs

I’ve been reading, and enjoying, Ann Finkbeiner’s The Jasons: The Secret History of Science’s Postwar Elite, an account of the Jason scientific advisory panel. One chapter details a Jason study that led to the deployment of two extremely low frequency (ELF) radio transmitters in Wisconsin and Michigan to communicate with submarines deep underwater:

Besides nonattenuation, ELF signals have two other relevant characteristics; they have the virtue of being unlikely to be disrupted by Argus-like nuclear explosions in the atmosphere; and they carry little information. Christofilos said this system would transmit six words per minute. He figured it would cost $138 million. Such an uninformative one-way signal is essentially a beeper; Jasons call it a “bell ringer.” The signals would be only of emergency-type signals, like “Go to hell,” said Ruina. Or, said a Jason, “My God, we’ve an atomic attack. Go and mutually assure destruction.”

All kidding aside, the ELF system broadcast three letter codes—as described by Douglas Waller in Big Red: Inside the Secret World of a Trident Nuclear Submarine—that didn’t seem to be authorization codes to launch nuclear weapons:

If the sub had to operate more covertly, still another wire antenna could be reeled out for two thousand feet to receive extremely low frequency (ELF) signals that penetrated deep into the water. The ELF signal came in agonizingly slowly, so the message consisted of only three letter codes. The shack had an inch-thick book in its safe that could translate each trigraph, often sent as a bell-ringer to order the sub to sail nearer the surface so it could pick up a lengthier message on another frequency.

The Emergency Action Message (EAM), according to Waller, contained much more information—four sets of instructions identifying the warplan indicating the number of weapons and targets; date and time window for attack; combination to the safe containing the launch keys and and an authentication code.

The ELF system, by the way, is being phased out.

FAS maintains an archive of unclassified Jason studies.


  1. Ann Finkbeiner (History)

    I’m delighted that you’re enjoying the book. The person who said “Go and mutually assure destruction” was the Jason with the longest and deepest association with the Navy. Other Jasons did say what you said, that the ELF signal just meant that the sub should come to the surface for more information, probably urgent. But all Jasons were very elusive about the whole subject and that Navy Jason should have been the most reliable source. I’d guess that either 1) what the signal meant changed with time; or 2) the Navy Jason was indulging his famous sense of humor; or 3) both. In retrospect, I could easily have added the phrase, “or come to the surface for orders.”

    As to the difference between your 3 letters and my 6 words, that’s probably again the difference in time: the 6 words came from a 1972 article by Nick Christofilos, the ELF system’s inventor. And who knows what “letters” and “words” mean in this context anyway? Somebody does, but not me.

  2. CAPT James Graybeal (History)

    Gen Cartwright, Commander U.S. Strategic Command, addressed our work to update the aging Nuclear Command and Control (NC2) in his Prepared Statement (pg. 17, for his 29 March testimony before the Strategic Forces Subcommittee
    Senate Armed Services Committee on Global Strike Plans and Programs. His priority is taking advantage of technology to move from a circuit based network to and Internet Protocol based network to deliver resilient air, land, and maritime Global Command and Control (GC2). This network will be available for use in situations beyond just NC2.