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MA-4245
Data encryption unit - wanted item - under construction

The MA-4245 was a data encryption/decryption unit, developed by Racal Datacom in Salisbury (UK) in the late 1970s. The unit was compatible with the MA-4153 Message Store of the PRM-4150 (TITHE) spy radio set. It was intended for use by Special Forces (SF) and Stay-Behind Organisations (SBO), and is housed in the same aluminium case as the MA-4230 burst encoder.

The unit is housed in a die-cast aluminium enclosure with two 5-pin Fisher connectors at the right hand side and all controls at the top surface. The control panel consists of 32 keys, 6 LED indicators and a 2-segment alphanumerical display at the top right.

The keyboard has a standard QWERTY layout with two characters on most of the keys. The LET-key (letters) at the bottom right is used to select the lower row of characters (A-Z), whilst the FIG-key (figures) at the bottom left is used to select the characters on the upper row (numbers and punctuation marks). Two additional keys at the right are used for CR and LF.
  
Racal MA-4245 control panel. Photograph suplied by Roman Brunecky [1].

At the top left are two keys marked EN (enable) and OFF. The OFF-key is used to turn the unit off after use. The EN-key is used to switch the unit on and to enable the extra commands on the upper row of the keyboard. Data can be entered after pressing the EN-key followed by PT (plaintext). Further instructions can be found on this page of the PRM-4150 technical manual [2].

Racal MA-4245 control panel [1] Sockets at the right side [1]

Versions
At least two different versions of the MA-4245 are known to exist. This is our current understanding of these variants:

  • MA-4245
    This is the basic version of the MA-4245. It has rectangular rubber keys on the alphanumerical keyboard in QWERTY arrangement, similar to the keys of the MA-4230 burst encoder. The key at the top left carries the full text 'ENABLE' and additional ← and → keys are located at the bottom left and bottom right of the keyboard.

  • MA-4245B
    This is a later version of the MA-4245 in which the rubber keys have been replaced by a membrane tactile switches. The size of the keys have been enhanced for easier operation and the ← and → keys are omitted. Furthermore, the key at the top left is marked EN.
References
  1. Roman Brunecky, Images of MA-4245 unit featured on this page
    Personal correspondence February 2015.

  2. Racal Tacticom, Use of the MA-4245B
    PRM-4150 Technical Manual. Part 1. Chapter 8. Appendix 2 (1 page). 1 May 1981.
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Crypto Museum. Last changed: Tuesday, 24 February 2015 - 15:32 CET.
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