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Secure Telephone Unit
The SECTEL 9600 was a secure telephone manufactured by Motorola in
Seguin (Texas, USA).
It uses Motorola's proprietary DVI encryption algorithm,
[3]
which offers a high level of security. It is classified as an
NSA Type 4 product,
which means it is for non-sensitive unclassified information, typically
intended for business applications. It is not
STU-III compatible.
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It offers two methods for key management:
manual mode, in which keys are generated by the system, and
automatic public key (APK) which offers a 'keyless' RSA-based technology for
exchanging the keys
[2]
.
The SECTEL 9600 is capable of sending voice and data simultaneously
at different speeds, depending on the quality of the (analog) telephone
line. A series of advanced speech processing algorithms have been implemented
to ensure superior voice quality at different speeds
[1]
.
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At 2400 baud, the SECTEL 9600 uses a 2.4 kbps Linear Predictive Coding
algorithm known as Enhanced LPC-10. It is based on the
FS-1015
or STANAG-4198 standard that is also used with the
Philips PNVX crypto phone.
It is suitable for both half and full duplex.
At 4800 baud, Code-Exited Linear Predictive Coding or CELP
is used in full-duplex, providing better audio quality.
At the highest speed, 9600 baud, an even better algorithm, called
Modified Residual Exited Linear Predictive Coding or MRELP,
is used in full duplex.
The SECTEL 9600 has a built-in V.24/V.32 modem that can also be used
for computer data at baud rates ranging from 75 to 9600 baud.
It is tested and compliant with most telephone systems around the world.
If the quality of the (foreign) telephone line is below average, the
system gracefully degrades to a lower speed, but maintains its Type 4
security.
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Although all STU-III telephones have now been discontinued and the
SECTEL unit itself is not classified, it is very difficult to obtain
information about this unit. Any information, such as the user manual,
is most welcome. If you can help us in any way,
please contact us.
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To suit the various customers and their safety requirements, different
SECTEL models were manufactured.
They all use the same enclosure and operation is more or less identical.
The diagram below shows the positioning of the various
SECTEL models.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Sunday, 02 October 2011 - 07:48 CET
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