We will be posting "tools of the cryptologic trade" periodically on this link. All visitors are invited to provide any information on how the tool was used by cryptographers. A summary of information received will be posted under the article. Please submit your unclassified, non-target specific comments to email@example.com, with a subject line of: Cryptographic Tool Challenge -- Attn: Dave D'Auria.
We are looking for information from any of our web site visitors who may know who, how, when and where this device was actually used by cryptographers, radio operators or other NSA/DoD personnel. The DoD transfer form attached to the unit describes it as a "National Security Telephone".
The artifact pictured is believed to be a 1950s era predecessor to today's modern secure phone system. It carries an NSA label of CE 62603 Subscriber Set No 1094, which designates it as "Communications Equipment" (CE) vice "cryptographic equipment" (KL). This subscriber set uses vacuum tube technology and may have been connected to a stand alone voice encryption device such as an early KY-3 or KG-13/HY-2 secure voice system. In tandem, it likely provided secure encryption for voice communications between facilities. The "CE" nomenclature was a designator often used by Bell Telephone and the DoD/US Army for their systems, which may point to the origin of this subscriber set. This particular set, in private hands, was shipped from an Army MARS Radio Station in Fredericksburg Texas to Kelly AFB is San Antonio. It may have been released from DoD inventory in 1974. We have a similar set in our Museum inventory with no other clarifying information.
The unit itself appears to be heavy gauge cast aluminum. The top has a carry handle/latch that when elevated & rotated loosens and removes the bolt that secures the top to the base. The interior is a heavy black plastic base with a center raised console. There is a a small speaker above the handset cradle. The handset is heavy black plastic with a conventional coiled cord that is connected to the left side of the console with a heavy duty mil-type Cannon/Amphenol-type connector. On the right side of the console is a phone jack. On the front of the console is a push-button labeled CALL and to its right is a black knob labeled VOLUME. The only possible external connection (perhaps to a stand alone encryption device) is a hole in the center of the bottom of the phone base.
The artifact pictured below is believed to be a WW II era Slidex code device. A Slidex is a manual encoding system used mainly for tactical communications to provide a short-term level of security when non-secure communication links are being used. They use a word or sometimes phrase substitution based upon a prearranged set of codewords or codephrases. The device pictured below came from the Lou Kruh collection donated to the NCM in April, 2010. It is about 8inches long by 4 inches wide. A wheel on the side rotates (i.e., "slides") the list of codewords forward or backward to encrypt usually short stereotyped messages. We are looking for information from any of our website visitors who may know who, how, when and where this device was actually used by cryptographers and/or radio operatiors.
The Slidex with which I'm familiar was a WW2 British tactical cryptosystem for tactical operations, regiment and below, combining the features of cipher and code, with the code vocabulary peculiar to intended service (staff, signals, supply, transportation, etc.). Probably from their Free French association with the Allies in WW2, the French in Indochina passed the system to their allies there in the 1950s, and it was known to the opposition. In the form with which I was acquainted, see
What you have pictured from Lou's collection appears to be more along the lines of a "handy-dandy" for radio/telephone operations than what I understand as the SLIDEX system per se. There is a website for WW II reenactors from Wireless Group Set19 that seems to have some restricted distribution stuff available on limited basis to its membership, but other SLIDEX references can be found using a Google search.
I can tell you this, from what I've read each day had a 'code' setting which was different for each division, and everyone (at least, most officers and signals personnel) in the division knew on each day what the settings would be for that day, and presumably for the next couple days. My guess is that these devices generally accompanied signals personnel and would have been fairly common in headquarters and observation posts.
So far, I've only seen one 'primary source' discussion of how this was used, and it comes from the 1st Division AAR for August 9th, 1944 (see photo of AAR below). A single American platoon at St. Loup (northeast of Mayenne) came under heavy attack and was forced to retreat. Apparently, the Slidex device was left behind and captured. Therefore, the division abandoned the Slidex settings for August 9th and 10th, and shortly before midnight all the subordinate formations were ordered to use the August 11th setting for the remainder of August 9th and August 11th.
So I think you will agree that at least this single source suggests two things: one, the Slidex was a tactical device likely to be seen at the tactical level, and two, its settings were generally determined by the division on a daily rotation.
1st Division AAR, August 9th, 1944
The 10 Point Divider (sometimes called an 11 Point Divider) pictured below came from the estate of a now deceased former cryptographer. In the public sector this "tool" is commonly used in drafting, form and textile design, model design, long range navigation, etc. We're looking for information from any of our web visitors who may know how this tool was used by cryptographers.
Comment by George on 5/16/10
The divider, and others like it (I have one) were used to manually transcribe data (1's and 0's) from analog displays and was used by both signals analysts (to find structure) and cryptanalysts (to obtain cipher). Time base jitter was a common problem and the higher the data rate, the more uncertain one was of the integrity of the stream. Use of these dividers often meant the difference between "no cipher" and "some cipher" until a system could be devised to automatically digitize the data.
Comment by Frank on 7/13/10
I used the 10 point divider in the 1960's in a signal analysis application to determine
presence of and to measure cyclic activity on continuous paper sonogram
displays. The 10 point divider came in different sizes from about 8 inches
in length to about 12 inches. In later years it became a handy tool to lay
out distances to scale on maps. This instrument may still be on display in a
corridor display case on the fifth floor on building 2A.
- Last Updated - 5/11/2013
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