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Burst encoders
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MA-4230 burst encoder and MA-4231 decoder

The MA-4235 was a complete system for encoding and decoding burst transmissions in morse code, developed by Racal Datacom Ltd in Salisbury (UK) around 1977 for use by Special Forces (SF) and for other special purposes. The complete set consists of an MA-4230 morse encoder, a complementary MA-4231 morse decoder, and an optional MA-4233 printer. The enclosure of the encoder and decoder units are identical, but the controls on the front panel are different.

The image on the right shows a typical pair. The unit in front is the MA-4230 morse encoder. The one at the back is the MA-4231 decoder.

Each unit measures only 175 x 120 x 50 mm and is housed in a die-cast aluminium enclosure. It weights about 1.1 kg and a rubber gasket makes the unit reasonably waterproof.

A special version of the encoder with an Arabic keyboard layout, the MA-4230A, was produced for the Iraqi Army in the period prior to the First Gulf War. It mates with the MA-4231A decoder.
Complete set

Each unit has two - rather special - 5-pin FISCHER sockets at the right side. These sockets are used for the connection between encoder and decoder, but also for the connection of a transceiver, a printer and a battery charger. A complete set of units can be connected to any standard Racal radio, by using an appropriate audio cable.

System using a Racal transceiver
When used in combination with a Racal transceiver, power is taken directly from the radio via the audio connector. In that case, no external PSU is needed. Connecting the set to other transceivers (i.e. non-Racal) is also possible. In that case a cable without an audio connector would be supplied by Racal, so that a suitable connector could be mounted later.

System using a non-Racal transceiver
In this situation, power can not be taken from the radio, and an external battery charger has to be used. This charger is generally connected to the MA-4233 printer at the end of the chain. It can however, also be connected to each individual unit in turn, under the batteries are fully charged. The following products are known in this series:

Designator Description NSN  
MA-4230 Encoder -  
MA-4231 Decoder -  
MA-4232 Battery charger -  
MA-4233 Printer 5865-99-539-6085  
MA-4230A Arabic version of the MA-4230 -  
MA-4231A Arabic version of the MA-4231 -  
MA-4233A Arabic version of the MA-4233 -  
MA-4235 Complete system (MA-4230, 4231, 4233, etc.) -  
ST450032 Line interface -  
ST450076 Battery charger -  

MA-4230 Morse Encoder
The MA-4230 is a small self-contained morse encoder. It consists of a die-cast aluminium case with 40 keys and 3 LEDs on it surface. It allows messages to be stored in its 1024 character memory, and sent in morse code at high speed (burst), in order to minimize the chance of interception and detection.

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MA-4230 morse encoder
MA-4231 Morse Decoder
The MA-4231 is an automatic morse receiver, designed to be used either stand-alone or in combination with an MA-4230 at the other end. In the latter case it can be used for the reception of high speed morse transmissions (bursts).

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Arabic version
This special version of the MA-4230 was made by Racal especially for the Iraqi Army just before the first Gulf War (1991). The MA-4230A has Arabic keys on the keypad and forms a pair with the MA-4231A burst decoder.

The MA-4230A unit is based on the same design as the MA-4230, except for a different keypad and different software.

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MA-4230A (Arabic version)

MA-4233 Printer
The MA-4231 morse decoder could be expanded by an (optional) external printer. Especially for this purpose, Racal developed a small ruggedised thermal printer. It connects to the decoder by means of 5-pin Fischer connectors.

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Another close-up of the printer
ST450076 Battery charger
When used in combination with non-Racal radio equipment, the ST450076 battery charger shown on the rights was used. It consists of a small metal frame with a transformer, fuse and power selector. The charger can be configured for both 115 and 230 V mains.

A short piece of wire with a 5-pin Fischer connector, allows the charger to be connected to the MA-4033 printer. Power is then looped through all units by means of the 5-pin interconnection cables.
ST450076 Battery charger

ST450076 Battery charger Typical Fisher connector
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ST450076 Battery charger
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Typical Fisher connector

MA-4235 Complete set
When examining the dimensions of the various module, one can't help noticing that printer is twice the size of the encoder/decoder units. In practice, a complete set consisting of encoder, decoder and printer could be built inside a standard briefcase such as Samsonite and Delsey.

Each unit has four 3 mm threaded holes at the bottom, allowing it to be mounted on, say, a metal base plate. The units could be arranges as shown in the image on the right, with the keyboard of the encoder at the bottom right and the readout of the decoder at the top right.

In this arrangement the printer is in the right position for ergonomic operation and all sockets are unobstructed, allowing the cables to run freely between the units. The charger (if present) would be mounted in the top lid of the briefcase.
Complete set
Complete set Complete set Complete set with printer open Operating the complete set Operating the complete set
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Complete set
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Complete set
3 / 5
Complete set with printer open
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Operating the complete set
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Operating the complete set

  1. Technical Manual MA.4230 MA.4230S Morse Encoder (with Battery Charger MA.4232)
    Racal-Datacom Limited. 1 October 1980, issue 1.10.80-100.

  2. Technical Manual MA.4231 Automatic Morse Receiver
    Racal-Datacom Limited. 2 February 1980, issue 2.2.80-100.

  3. Conversion notes for the Racal MA4230/4231
    John's Radio, Conversion from Arabic to English. Date unknown.
  1. Army Radio Sales Co, Racal MA-4230A and MA-4231A
    Retrieved June 2009.

  2. Jane's Military Communication 1986, MA 4233 Minature Printer
    p. 453/454. ISBN: 0-7106-0824-1
Further information
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Crypto Museum. Created: Thursday 26 August 2010. Last changed: Saturday, 01 July 2017 - 11:13 CET.
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