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Telsy Cryptophone 7000
Digitally encrypted telephone

The Cryptophone 7000 was a secure telephone for use on analogue networks (PSTN), with fully digital encryption and decription of speech and fax data. It was developed and manufactured in 1990 by Telsy in Turin (Italy) as the succesor to the successful 1st generation KV-3000 series.
 
The Cryptophone 7000 was an all-in-one solution and was only slightly bigger than a standard telephone set. It came in a black or white case, and had an extremely clear and intuitive user interface with 12 push-buttons and a crisp 2 x 40 character LCD display.

The image on the right shows a typical Telsy Cryptophone 7000 with its handset on-hook. The display shows the name of the phone, plus the current date and time. A tiny little physical key to the left of the push-buttons is used to select the required mode of operation.
  
Telsy Cryptophone 7000

The 2nd generation Cryptophone 7000 uses Digital Signal Processing (DSP) technology and hardware-based encryption. It was successfully sold to the Government and Corporate sectors, but was also sold as an OEM product by various ICT Security suppliers. The Cryptophone 7000 remained in production for many years, until is was succeeded in 2005 by the 3rd generation Cryptophone T3 which is still available from Telsy today (2012).
 
Telsy Cryptophone 7000 Clear-voice mode Removing the key Mode selector (key) Clear-voice mode Setup mode Locked mode (outgoing calls blocked) Entering Config-mode

 
Operation
Operating the Telsy Cryptophone 7000 is extremely easy and intuitive. All user I/O is via the keyboard and the LCD-screen. Voice communication is possible via the handset, or hands-free via the built-in speaker (top) and microphone (front). The unit can hold up to 16 different cryptographic keys, each of which is identified by a label (i.e. a name) for authentication.
 
The small key, to the left of the keyboard, is used to select the operating mode. It has three positions (from left to right):
  • L: Setup
  • M: Operation (normal)
  • R: Locked (incoming calls only)
The cryptographic keys can be entered in Setup-mode, using the SET-KEY function. Each key consists of 16 digits (0-9) plus an optional label, consisting of up to 8 alphanumerical characters. From this the phone calculates an identifier.
  
Mode selector (key)

Once the cryptographic keys have been programmed, all the user needs to do is dial the other party, talk in clear, and then press the CR-button. The Cryptophone 7000 at both ends will then synchronize and look for a common key (i.e. a key that is known by both parties). If such a key is found (i.e. the identifier matches), both phones switch to secure mode (CRYPTO).

If no common key is found, a dialogue appears on the LCD-screen to indicate that a RANDOM CRYPTO KEY will be used instead. Such a random key is only valid for a single session and cannot be intercepted by a third party. In this mode, authentication of the other party is not possible.
 
Full-duplex and half-duplex
By default, the Cryptophone 7000 works in full-duplex mode, which means that the user can speak and listen at the same time. Under certain circumstances, e.g. when the line is too bad, the unit can switch to half-duplex, which means that only one partly can speak at a time. This is also the case when the Cryptophone 7000 is used over a satellite link.

In half-duplex mode, the change-over of direction (i.e. the transmitting party) is voice-controlled (VOX). In noisy environments however, the #-key (bottom right of the keyboard) can be used to switch to manual operation. In this case the #-key is used as the Push-To-Talk switch (PTT).
 
The interior of the Cryptophone 7000 can easily be accessed by removing six bolts from the bottom of the unit. The top half of the case can then be removed and the interior becomes visible. At the left is the telephone interface with a Siemens PSB4506 speech circuit [3].

The keyboard is mounted on a separate board that is held in place by 6 small plastic snaps. It can easily be removed and folded aside, so that the digital circuitry becomes visible. The PCB is very well designed with a good eye for detail and Electro-Magnetic Compatibility (EMC).
  
Microprocessor and peripheral chips

In fact, the design is much better than, for example, the US CVAS-III crypto phone of the same era. The Cryptophohe 7000 has a professional quality PCB with sufficient ground planes. At the left are two AT&T T-7522 codecs that are used for full-duplex speech encoding and decoding.

At the right is the microprocessor with its EPROM and other peripheral chips, shown above. At the heart of the digital circuit are two Texas Instruments TMS-320 Digital Signal Processors [4], of which the leftmost one is an EPROM-version. All programmable and critical ICs are in sockets and can easily be swapped. The firmware of the Cryptophone 7000 was updated several times.
 
Cryptophone 7000 interior Circuit below the keyboard Digital circuit with DSP at the center The two AT&T codecs (full-duplex) Microprocessor and peripheral chips A Siemens telephone interface

 
References
  1. Telsy S.p.A., Cryptophone 7000 - THANKS !
    Device featured on this page kindly donated by Telsy. April 2012.

  2. Telsy S.p.A., Cryptophone 7000 User's manual
    1st issue, 23 April 1990.

  3. Siemens, Enhanced Speech Circuit (ESC) PSB 4506
    April 1992. Retrieved May 2012.

  4. Texas Instruments, TMS320 Second-Generation Digital Signal Processors
    May 1987. Revised November 1990. Retrieved May 2012.

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Crypto Museum. Last changed: Thursday, 03 May 2012 - 13:58 CET.
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