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Racal MA-4225
Portable voice scrambler - under construction


MA-4225 is a portable frequency- and time-domain (F/T) voice scrambler, also known as a two-dimensional secure speech device, introduced in 1983 by Racal COMSEC in Salisbury (Wiltshire, UK). The device is bascially a miniaturised version of the MA-4224, with which it is compatible.

The device has roughly the same dimensions as a handheld radio of the era, and allowed secure voice transmissions over regular narrowband voice circuits, such as VHF and UHF radio links and regular (analogue) telephone lines (POTS).

The device measures 270 x 90 x 30 mm and weights 952 grams, battery included. At the top is a MODE selector, an red indicator and sockets for connection of a handset and a radio. At the front is a 17-button keypad that can be used for entering the key(s). It is compatible with the MA-4224 and with the MA-4400 secure telephone.
  
Keypad at the front of the MA04225

Judging from the manufacturing date-codes on the various chips on the PCB, the unit shown here was manufactured around 1984. The design is based on the earlier MA-4224, of which the many discrete logic circuits have been combined into a single LSI chip — the RACAL RMSL — whilst the analogue circuits were built in hybrid technology on ceramic substrates, in order to save space.

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Bare MA-4225 unit with protective cap at the bottom MA-4225 secure voice unit MA-4225 with battery fitted MA-4225 and separated battery MA-4225 with battery Battery Keypad at the front of the MA04225 MODE selector, indicator and connections at the top of the MA-4225
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Bare MA-4225 unit with protective cap at the bottom
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MA-4225 secure voice unit
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MA-4225 with battery fitted
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MA-4225 and separated battery
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MA-4225 with battery
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Battery
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Keypad at the front of the MA04225
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MODE selector, indicator and connections at the top of the MA-4225

Interior
The MA-4225in the palm of a hand Interior Hybrid building blocks Keypad PCB
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The MA-4225in the palm of a hand
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Interior
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Hybrid building blocks
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Keypad PCB

Specifications
  • Dimensions
    192 x 90 x 30 mm (270 x 90 x 30 mm with battery)
  • Weight
    658 g (952 g with battery)
Documentation
  1. Miniature Encryption Unit MA 4225, Technical Manual
    Racal-Comsec Ltd. TH-1156, Issue 2, December 1985.
Further information
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Crypto Museum. Created: Monday 13 September 2010. Last changed: Monday, 02 March 2020 - 20:09 CET.
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