A Call to Former KL-7 and KL-47 Operators

TSEC/KL-7 © Dirk Rijmenants

The TSEC/KL-7 crypto machine was developed by the Army Security Agency (ASA) and Armed Forces Security Agency (AFSA) under the name AFSAM-7 and introduced in 1953 by the National Security Agency (NSA) into the U.S. Army and Air Force, and later also into the CIA and FBI. The machine also served in all NATO forces, their embassies and some state departments. The U.S. Navy AFSAM-47B, later known as the TSEC/KL-47, was compatible with the KL-7. The last machines  retired in the early 1980s. It's been little over 40 years ago that the last machines left the service and time is running out to document first-hand accounts on these machines.

If you are a retired signals veteran with experience on the KL-7 or the KL-47, as operator or technician, a member of a signals association or organization, or worked in the communications section of a state department that used the KL-7, then contact us through our website to document your story. The KL-7 is fully declassified, and we're not interested in classified information, we only want to preserve the cryptologic history of these Cold War icons.

Besides the United States, the KL-7 was also used by its NATO allies Australia, Belgium, Canada, Denmark, England, France, Germany, Greece, Italy, Luxemburg, the Netherlands, Norway, New Zealand, Portugal and Turkey. Outside NATO, the KL-7 was also on loan to South Korea, South Vietnam and Taiwan. If you're a signals veteran from any of these countries, a state department or embassy in the 1950s to 1980s era, then contact us, or spread the word.

Unfortunately, time is running out to document first-hand accounts, as the people involved are age seventy or older, and memories fade. Please share this request with all signals communities that might have former KL-7 or KL-47 operators and technicians. Those who share their story retain full control over the content and how it is published.

Let's preserve cryptologic history!

Visit the U.S. TSEC/KL-7 ADONIS & POLLUX webpage to learn more about the KL-7, its development, technical details and full history, including some first-hand accounts, also shown below, to get an idea of the kind of stories we hope to document. You can contact us through the contact page on our website Cipher Machines and Cryptology.

• History of the TSEC/KL-7 ADONIS & POLLUX (full history)
• KL-7 in Vietnam - COMSEC Support at Air Base Saigon
• OTT Mixers and the KL-7 at NATO in West Germany
• The KL-7 on Merchant Ships during the Falklands War 
• More SIGINT Chatter blog posts on the KL-7

Enjoy reading!

Martin Gillow's Virtual Colossus and Other Machines

The Virtual Colossus
© Image Martin Gillow

The history of crypto equipment is quite fascinating, but diving into the archives, searching for historical publications, or collecting those old machines is not everyone’s cup of tea. Luckily, we have a community, dedicated to preserving the history of old crypto equipment, research the technical details, publish their history and operational use, and bring those old crypto machines back to life, either physically, which can be quite expensive, or virtually though software simulations.

Writing software that works exactly like the real crypto machine requires extensive study of the original machine, its mechanical and/or electrical properties, and many hours to write the software that reproduces the plaintext or ciphertext exactly like the original machine. However, you could take it one step further, and make a virtual three-dimensional machine where you can manipulate all components and encrypt, decrypt or break messages, just like the wartime operators.

Martin Gillow created a website with no less than ten 3D simulations. The virtual British Colossus machine is the first ever digital computer, developed in WW2 to break the German Lorenz SZ40/42 encrypted telex, of which he also created a virtual version. There’s also the virtual Enigma machine, and the Bombe that was used by the Bletchley Park codebreakers to decrypt the German Enigma messages.

Hagelin's U.S. M-209
© Image Martin Gillow

Also the British Typex machine and the U.S. M-209, developed by the renown Swedish engineer Boris Hagelin, have their 3D version. Moreover, the collection includes the ICT 1301 ”Flossie” second-generation computer, the E.R.N.I.E electronic random number generator, and the American crib dragging machine Dragon that helped to break the Lorenz messages.

Of course, the countless hours of work by Martin to research and study those machines, and write accurate 3D versions, is just enormous, and makes this 3D collection simply unaffordable… unless you just want to preserve and share the history of old crypto machines, and make the simulations available to everyone for free. A big Thank You to Martin for creating all those virtual machines, and for being part of that small community, dedicated to preserve cryptologic history.

Make sure to scroll all the way down his main page, to find all virtual 3D simulations and read the various tutorials on how to use them. Also click the relevant "find out more" buttons to learn about each machine and its history. Visit the Virtual Colossus website.

 

Highly recommended, and no better day than D-day to share Martin's work and commemorate all codebreakers.

Ringway Manchester

Ringway Manchester

The Ringway Manchester YouTube channel is a fascinating journey into radio waves, but hard to describe, as it covers so many subjects with signals as the common theme. Lewis created hundreds of videos on various signals from across the world and explains the equipment and historical context behind them.

No extensive documentaries, but interesting bite-sized 5 to 15 minutes videos about shortwave listening, numbers stations, military transmitters, pirate radio, Cold War relics, clandestine radios and spies, transmitter locations and mysterious and even frightening signals, but also reviews of transceivers, receivers and handheld scanners.

Click banner to visit the YouTube channel

Visit also Lewis Ringway Facebook, RingwayManchester X (Twitter) and M3HHY Instagram, well worth following.

Below some Ringway Manchester videos that might want you to buy a shortwave receiver and start surfing the radio waves. Many more videos available at his YouTube channel. Enjoy listening!

Everything About Numbers Stations and How To Listen

 

Radio Systems At The Former Largest US Military Base In Europe

 

The Most Terrifying Shortwave Signal Ever

 

Secret Shortwave Signals That Remain An Unsolved Mystery

The First Compiled History of the KL-7

TSEC/KL-7 © Dirk Rijmenants

The TSEC/KL-7 was the first rotor cipher machine to use electronics, and although the KL-7 had excellent cryptographic properties, its track record is what made this machine a true Cold War icon. My first encounter with that curious unknown machine with vacuum tubes was back in 2005 in London on the battleship HMS Belfast, displayed behind glass.

It took another six years to unravel the inner workings of this cryptologic beauty, and write the first accurate KL-7 simulator. This was only possible thanks to the release of many technical documents from the National Security Agency (NSA), through Freedom of Information Act requests (FOIA's) from Bill Neill, and published by Nick England from US Navy Radio Communications. The technical expertise from Paul Reuvers and Marc Simons from the Crypto Museum, and from George Mace, were also instrumental to develop the KL-7 simulator.

However, despite the release of some history related documents, only fragmented pieces of its development and operational use were available, and the history of the KL-7, initially named AFSAM-7, remained largely unknown to the public. In the last three years, I could connect more dots, found in the NSA's William Friedman records.

Historical records from the U.S. Army Security Agency (ASA) contained production details, planning and procurement, and later described the analysis of the KL-7's use in Vietnam. Those records were preserved by the NSA. The NATO archives revealed the use of the KL-7 by many allied countries and some of their state departments, and the technical support they received.

Although there were only unconfirmed hints that the KL-7 was also used by the CIA and FBI, some tiny bits of information provided clues on where and how to search for more information. Moreover, ASA records confirmed the procurement for those agencies. That search took long, but eventually led to a few CIA documents, multiple FBI files, and letters from FBI director J. Edgar Hoover that confirmed their own use of the KL-7, and its use by the White House, on the presidential airplane Air Force One, and several Asian countries.

The KL-7 also has its own chapters in the history of Cold War espionage, with chief warrant officer John Walker selling the machine's technical details and secret keys lists to the Soviets, but the Counter Intelligence records from the Director of National Intelligence (DNI) also detailed warrant officer Joseph Helmich's betrayal, leading to other FBI files on counterintelligence operation Hookshot to catch Helmich. His case is less known than John Walker's, but just as interesting.

Ever more pieces of information were added to the KL-7 webpage, which already contained all technical information, making it quite large. To make the KL-7 history more accessible, I decided to publish the article that I started in 2022, which also includes references to the relevant ASA, AFSA, NSA, NATO, FBI, CIA and DNI files. This way, everyone can easily find all related files for their own research.

Since my motto is "history is here to share", you're free to share or publish the below document, or parts of it, provided that proper credits are added. Why should you share it? Because its use across the world for decades, and the spy cases, make the KL-7 a true Cold War icon that deserves its place in history, but also to honor the cryptologists and engineers who developed this marvel, and the operators who served around the world, lest we forget.

History of the TSEC/KL-7 ADONIS & POLLUX - The first standard U.S. tactical lightweight rotor cipher machine using electronics (pdf)
(latest update May 14, 2026 Version 6.1)

If you're also interested in how the machine works, its development and full history, then visit the TSEC/KL-7 page at the website.

Call to Veterans! If you operated or maintained the KL-7, we're always interested in your experiences with the machine to expand its history. We're not interested in classified information, only stories about where and how you worked with the KL-7 (the machine is declassified). Since the KL-7 retired more than 40 years ago, time is running out to document stories. If you have a story to share, then contact us through the contact page on our website Cipher Machines and Cryptology.

Let's preserve cryptologic history!

To get an idea of the kind of stories we would like to document, check out these already published stories, also available at the website:

• KL-7 in Vietnam - COMSEC Support at Air Base Saigon
• OTT Mixers and the KL-7 at NATO in West Germany
• The KL-7 on Merchant Ships during the Falklands War 

Enjoy reading!

RN Communications Branch Museum/Library

HMS Mercury
Royal Navy Signals School

Sometimes you need serendipity to discover a fascinating website. I researched the TSEC/KL-7 cipher machine for long, and was able to find the few declassified documents on this 1950s cryptologic gem that served until the early 1980s.

Initially named AFSAM-7, the KL-7 was developed for all US armed forces, but the US Navy developed its own fully compatible version with a few more options, named AFSAM-47B, later designated KL-47.

Unfortunately, little is known about the British use of the KL-7. However, several NATO documents linked Royal Navy patrol boats, minesweepers and submarines to the KL-7 instead of the naval KL-47. The search engine keywords KL-7 and Navy, and a bit of serendipity, lead me to the RN Communications Branch Museum/Library.

This fascinating website is a private initiative from Ken Sutton, who served from 1966 until 1998 in the Royal Navy (RN) and retired as Warrant Officer 1st Class. He then served as civilian Communications Training Design Officer until 2012.

RN Comms Museum History  

The museum/library has existed since the late 1800s when the RN Signal School was based in the RN Barracks Portsmouth, now HMS Nelson base. In 1941 the Signal School and its library moved to the HMS Mercury shore establishment near Petersfield, where the library was maintained and a small museum was established.

HMS Mercury closed in 1993 and moved into HMS Collingwood shore establishment in Fareham. Unfortunately, no space was allocated for the Mercury museum and library, leaving all exhibits kept in cupboards and drawers. The Royal Navy Signals history comprises several branches and specific expertises, of which the communicators were the workforce, and still are today.

The badges of Tactical, Women's Royal Naval Service and Telegraphist/Sparkers

The first badge (crossed flags) is the Tactical badge, the branch that dealt with all comms by flashing light, semaphore, flag hoists, with expertise in the manoeuvering of ships. This side of the branch was transferred to the Seaman Specialist branch circa 2004. 

The second badge (blue gold wings) is the Telegraphist/Sparkers badge of Women's Royal Naval Service (WRNS) Communicators from the era that WRNS served mainly in shore communications centres worldwide. Few were morse trained and most trained in message handling. They also were trained to encipher and decipher messages using various systems. Notably, they also made up the majority of GC&CS personnel in Bletchely Park during WWII. They eventually integrated in the RN and now serve aboard navy vessels, informally still known by the nickname "wrens".

The third badge (gold wings) is the Telegraphist/Sparkers badge of the branch that dealt with all radio communications.  Today, this branch is referred to as the Communication and Information Systems branch (CIS) due to the amount of computerised systems used in the communications world.

Preserving History   

When Ken Sutton retired in 2012, he volunteered to set it all up again.  The museum is not an official RN museum, even though it resides in a naval establishment.  He created the website to make the museum's exhibits and documents available to all RN Communicators past and present without having to travel long distances to visit it.

His small website turned into a major project when Jeff Dykes, a former Warrant Officer Radio Supervisor, requested Ken to incorporate his huge online archive about all things Navy into the RN Comms Museum website. That's where I found the first account from Royal Navy personnel on the KL-7 and its use.

The website has a huge collection of technical information about naval communications, transmitters and receivers, technical drawings and photos, but also about how the Royal Navy is organised, from information on submarine warfare to burial at sea. You name it, and there's a page about it. Now, back to the KL-7...

The RN Comms Cryptography page describes in detail the KL-7 and its early use in the Royal Navy. More about the KL-7 and how it was used at the Cold War Cryptography page.

Do visit the RN Communications Branch Museum/Library and make sure to check out the Sparkers and Snippets menus, each of which has several sub-menus with many more pages, hundreds! Use their Search Page to find specific items in the vast collection.

Highly recommended!