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MEROD Base Station

The MA-4420 was a base station for messages sent and received by MEROD devices, developed by Racal COMSEC in the early 1990s. It was at the heart of a message center that allowed secure messages to be sent, received, recorded and printed. The MA-4420 is known to have been used by several UK services, including the Army, Special Forces (SF) and Diplomatic Services.

The image on the right shows a typical MA-2240 unit as it was used with the Dutch Special Forces during the 1980s. The unit is housed in a 3U 19" rack mount case with a Power Supply Unit (PSU) bolted to the rear; a rather heavy black 'blob'.

All controls and indicators are on the front panel, whilst all connections are placed at the rear. Once powered up, the mode of operation is selected with the KESO key at the center. It has four positions: RUN A, RUN B, TEST and RESET. In case of compromise, the user would press the CLEAR KEYS button to delete the crypto keys.
Racal MA-4420 MEROD Base Station

The diagram below shows the position of the MA-4420 in a possible configuration. At the left are the MEROD units used in the field in combination with a manpack radio. At the right is the message base station. The MA-4420 is at the heart of the message center. All connections to other equipment are at the rear.

The following connections are available: REMOTE, IEE 488, Printer, Radio 1, Radio 2 and Clear Keys (Zeroize). The printer connector is a DB25 male socket that is probably wired for a standard parallel (Centronics) printer. The IEEE connector is probably used for external control by a PC, which is a rather common standard. The pinout of the REMOTE connector is currently unknown.

Racal MA-4420 MEROD Base Station Indicators MODE selector key switch ALARM RESET button ZEROIZE button Rear panel connections Rear panel connections Power Supply Unit (PSU)
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Racal MA-4420 MEROD Base Station
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MODE selector key switch
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ZEROIZE button
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Rear panel connections
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Rear panel connections
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Power Supply Unit (PSU)

Dutch Special Forces
The MA-4420 was also used by the Dutch Special Forces (Corps Commandotroepen). In The Netherlands, the device was known by its Army-designator KY-5589/TGC-5578. It is also known as NSN 5830-99-777-0457. In the field, the Dutch SF used MEROD terminals connected to an AEG Telefunken SE-6861 manpack radio, as shown in the image below.

In the picture, a Dutch SF (Commando) operating from un underground hideout is entering a message on his portable MEROD device. The SE-6861 radio is at the top right. A candle at the top left is used to illuminate the scene.

In The Netherlands the radio was commonly known as LAPR (Lange Afstand Ploeg Radio, Long Distance Group Radio) and the MEROD device was called DBA (Digitaal Berichten Apparaat, Digital Message Device). The set was dropped in the early 2000s, when it was replaced by Harris equipment.
Dutch Special Forces using MEROD in the field

Help required
At present we have no further information about the MA-4220. If you now anything about it, or if you have a user manual or circuit diagrams, please contact us. You help is much appreciated.

  1. Racal-Comsec, MEROD, A Military Data Communications System
    Full colour brochure of MA-4420 MEROD Base Station. Date unknown.

  2. Jane's Military Communications 1988, MEROD MA4420 Base Station
    pp. 438-439.
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Crypto Museum. Created: Saturday 31 December 2011. Last changed: Saturday, 24 February 2018 - 16:43 CET.
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