Click for homepage
1500 →
Motorola SECTEL
Secure telephone unit · STU-III

SECTEL was a range of secure telephones for use on analogue PSTN networks, manufactured by Motorola in Seguin (Texas, USA). Some SECTEL models are STU-III compatible and are based on the 1986/1987 STU-III standard, developed by the US National Security Agency (NSA). Different models were manufactured with a varying degree of security, ranging from Type 1 to Type 4 NSA encryption products [1]. The NSA Type 1 versions were for exclusive use by the US Government. 1

The devices are housed in a black or cream plastic enclosure and are only marginally bigger than a regular desktop telephone set of the era. At the left is a cradle with a common handset. To its right, close to the front edge, is a keypad for dialling the numbers 0-9 plus the '*' and '#'. Towards the rear is a large Liquid Crystal Display (LCD) with 16 pre-defined function keys plus another 16 user-definable short-cut buttons.

At the right side, towards the rear of the unit, is a receptacle for the Crypto Ignition Key (CIK), which is a Datakey KSD-64 Key Storage Device.

The devices use a variety of vocoders (CODECs) and encryption algorithms, depending on their classification level. The image above shows a typical black Motorola SECTEL 2500, which is an NSA Type 2 device. Note that only the SECTEL 1000 and 2000 series are STU-III compatible.

  1. And the Canadian Government.

Motorola SECTEL phones on this website
Motorola SECTEL 1500 (Type 1 encryption)
Motorola SECTEL 2500 (Type 2 and 3 encryption)
Motorola SECTEL 3500 (Type 3 encryption)
Motorola SECTEL 9600 (Type 4 encryption)
Motorola STU-II/B SECTEL (NATO-version)
Motorola STU-III/R
Strictly speaking, STU-II/B and STU-III/R are not SECTEL products, but since they are based on the same Motorola hardware development, we are listing them here as well.

SECTEL models
To suit both the safety requirements of the customers and US Government regulations, different SECTEL models were manufactured, all based on the same basic hardware design and enclosure. The firmware and the cryptographic algorithms are different however. The diagram below shows how they are positioned. Only the SECTEL 1000 series and 2000 series are STU-III compatible.


Type 1 products use classified (secret) NSA encryption algorithms and are intended only for use by the US government and some allies, at the highest level of classification. Type 2 products use classified algorithms endorsed by the NSA, and are used for protection of sensitive information between government agencies. Approval from the US or Canadian Government is required.

Type 3 products use an unclassified, fully public encryption algorithm that is used for protection of sensitive or company-proprietary information. Type 3 is also referred to as NIST Standard DES. It is only sold to US government contractors and approved companies. The SECTEL 3500 is an example of a Type 3 product, whilst the SECTEL 2500 can use both Type 2 and Type 3 encryption.

The SECTEL 9600 is the only phone in this family that uses Type 4 encryption. It is intended for unclassified, non-sensitive information between companies. It uses a non-classified, publicly available and fully published encryption algorithm. It could be sold to all countries except those that were on the US proscribed list, but was never a commercial success.

 More about NSA encryption products

Presidential communication
For a president, communication with his ministers and advisors is paramount. In the past, the STU-III has proved to be a major 'lifeline' for various presidents whilst travelling through the country or during overseas visits. Generally, a couple of STU-III phones were installed by the US Secret Service, at any likely or unlikely location that the president could possibly visit that day.

The STU-III has an analogue interface and can be connected to a POTS telephone wall socket any­where in the world, allowing secure conversions over non-secure telephone lines up to the level of TOP SECRET. For this reason, the later STE phone still supports analogue connectivity.

The long life-span of the STU-III is illustrated by the fact that it served four US Presidents: Ronald Reagan, George H. W. Bush (Sr), Bill Clinton and George W. Bush (Jr). Although it not certain, it is possible that the suceeding president, Barack Obama, also used the STU-III secure telephone.

The STU-III was gradually phased out between the mid 2005 and 2009, during the tenure of Barack Obama, the 44th US President (2009-2017). It was replaced by the STE, of which the first versions were backwards compatible with the STU-III.

 More about the STU-III

Model NSA 1990 [1] 2004 [5] Remark
SECTEL 1500 Type 1 $ 1800 $ 2845 STU-III
SECTEL 2500 Type 2 $ 2145 $ 3395 STU-III
SECTEL 3500 Type 3 $ 3395 ? DES
SECTEL 9600 Type 4 $ 4495 ? DVI
STU-III/R Type 2 ? $ 8227 STU-II and STU-III compatible gateway
  1. Robert Crotinger, Motorola STU-III Fact Sheet

  2. Eric Draper, Photographs of President George W. Bush during the 9/11 attacks
    AP Photo/The White House. 11 September 2001. Retrieved, June 2011.

  3. National Security Agency, Cryptologic Excellence: Yesterday, Today and Tomorrow
    Brochure at the event of the 50th anniversary of the agency 1952-2002. p. 16.

  4. National Security Agency, Photograph of George W. H. Bush using a STU-III phone
    NSA Website. Retrieved February 2013.

  5. TSG, Approved Telephones - Pricelist
    TSG Standard 6, July 2005.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Sunday 11 July 2010. Last changed: Monday, 16 January 2023 - 13:29 CET.
Click for homepage