The AN/FRC-117 Survivable Low Frequency Communications System (SLFCS) was a communications system designed to be able to operate, albeit at low data transfer rates, during and after a nuclear attack.[1] The system used both very low frequency (VLF), and low frequency (LF) radio bands.


SLFCS was used for United States nuclear forces' command and control communications for Emergency Action Message dissemination and force direction. Single channel, receive only capability was provided at ICBM launch control centers. The single channel operated between 14 kHz and 60 kHz to receive commands from remotely located Combat Operations Center – Transmit/Receive (T/R) sites; this low frequency range is only slightly affected by nuclear blasts.

SLFCS' primary advantage was that it would experience minimal radio signal degradation as a result of nuclear detonations. It would be an alternate means of communication during and after detonations, providing a survivable command and control communications network for the Strategic Air Command (SAC), the Joint Chiefs of Staff (JCS), and North American Aerospace Defense Command (NORAD). SLFCS would also relay signals from the Navy's LF/VLF systems.




See also: Green Pine (communications)

The GREEN PINE communication system took messages broadcast over SLFCS and 'upconverted' them to UHF messages for bombers headed north. There were a handful of GREEN PINE stations in the northern portions of Alaska and Canada.[2][3]

Receive Only


The first program (487L) took six years from the time of the initial requirement to full operation. The second part (616A), which was basically a modification of an already operational system, took 10 years.


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See also


  1. ^ (2005-04-28). "Survivable Low Frequency Communications System (SLFCS) – United States Nuclear Forces". Retrieved 2007-10-04.
  2. ^ Strategic Air Command Regulation 100-24 Vol III: SAC Communications System Operations/EWO Support Requirements, 6 Jul 1979
  3. ^ Santa Barbara Amateur Radio Club Key Klix: "Survivable LF Comm System", April 2008, Vol 55, No. 4
  4. ^ a b c Air Force Historical Research Agency: "History of 3902d Air Base Wing, July – September 1968"
  5. ^ Selnick, D., "Higher Authority Communications/Rapid Message Processing Element (HAC/RMPE)", 2002
  6. ^ Air Force Space Command: "Minot completes final MEECN modifications", 17 Nov 2005 Archived 24 March 2010 at the Wayback Machine