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Siemens DSM Voice
Telephone voice encryptor

The Data Security Module (DSM) Voice is a digital encryptor for analogue telephone lines, developed by Siemens in Munich (Germany) around 1996. The DSM Voice is connected between the telephone unit and the network, and uses a smart card for authentication.

The DSM Voice unit is normally placed aside a standard telephone set. At the rear it has connections for the telephone, the line and the external power supply unit (PSU). The control panel consists of an LCD display, 3 LEDs and a single button. A typical unit is shown here.

A smart card slot is present above the display. The card (shown here) is used for authentication as well as public key exchange. Once the smart card is inserted into the device, secure mode (crypto) is activated simply by pressing the button on the control panel. Call partner authentication and the creation of a new session key for each call, are performed automatically.
Siemens DSM Voice with chip card

MRCELP vocoder technology is used to provide good quality speech in encrypted mode. The DSM Voice is only suitable for speech (voice calls). Alternative DSM units were available for other types of data, such as DSM Fax, DSM X.25, DSM Link and DSM ISDN [2]. At present, no further information about these units is available. If you know more about the Siemens DSM family of devices, or if you happen to have user manuals, please contact us.

Control panel Smart card and DSM Voice unit DSM Voice unit and smart card Inserting the smart card DSM Voice unit with smart card present Siemens DSM Voice with chip card Connections at the rear DSM Voice with PSU
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Control panel
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Smart card and DSM Voice unit
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DSM Voice unit and smart card
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Inserting the smart card
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DSM Voice unit with smart card present
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Siemens DSM Voice with chip card
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Connections at the rear
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DSM Voice with PSU

  1. Barry Wels
    Donator of the Siemens DSM Voice featuered on this page.

  2. Jane's Military Communications 1997-98
    ISBN: 0-7106-1530-2. p. 532
Further information
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Crypto Museum. Created: Wednesday 06 February 2013. Last changed: Saturday, 24 February 2018 - 17:58 CET.
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