Brent Secure Telephone System
The Brent secure telephone system comes in several varieties.
The basic model was colloquially known as an 'X21 Brent' . It had
no direct dial interface, but was dialed via an external Terminal
Adaptor that basically put the X21 on-line to the other Brent.
The second version was an 'ISDN Brent' which plugged into a
standard UK ISDN line, thus giving it capabilities of clear voice,
secure voice and secure data.
The third was a Brent 2, which was a ISDN Brent, with a Red S0 on
the rear which gave the Brent 2 a 'dial though' capability for ISDN
products (so one can do secure ISDN video conferencing for example)
via the Red S0.
The Brent 2 also came in two sub variants called 'Lector and
Hannibal' . It was manufactured by Marconi Space and Defense.
The Secure Telephone Key (STK) was the 'fill' and it was inserted
in the right hand side. One had to turn it a quarter of a turn
clockwise to engage it. The STK was basically an EEPROM.
The STK's came in basically 8 variants. Number 0 was Voice.
Anything greater than that was classified as a 'Super STK' which
also came with a pin code book. One had to type in a specific PIN to
get the key to function.
Also, the STK also identified the user so that the remote party
had an idea who was calling. Therefore when receiving a secure
telephone call, on the LCD display, you would see the name of the
remote party - e.g 'HMS' Unpronounceable.