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Racal MA-4777   Cougar
Voice encryption unit

The MA-4777 was a voice encryption/decryption unit, developed by Racal Ltd in Bracknell (UK) around 1987. It was intended for use in combination with Racal Cougar radio sets, but was also used with other transceivers, such as the VRC-8000. The MA-4777 was produced until 2001.
 
The image on the right shows a typical MA-4777C. The device is housed in a ruggedized green metal enclosure. At the front is the connection for the handset. In the MA-4777C this is a 6-pin U-229 socket for connection of a standard US or NATO handset or headset.

On the MA-4777A, a military 7-pin socket, similar to the one at the rear panel, is present at this location. It is for connection to Clansman equipment. The connector at the rear is for connecting the MA-4777 to a transceiver, using an adapter cable that is suitable for the radio.
  
MA-4777C

The only controls that are available on the MA-4777 are the two rotary selectors on the front panel. The upper one is for setting the audio volume, whilst the lower one is used to select one of four key compartments, marked A, B, C and D. Clear speech is selected by setting the lower switch to the Clr-position. Setting both switches to Z, purges the keys (see below).

Production of the MA-4777 started around 1987 with the MA-4777C. Over the years, the design was improved and simplified several times, but the Crypto Module remained the same. The latest version is the MA-4777A, which was produced from 1994 until the end of its life cycle.
 
MA-4777C MA-4777C Small portable unit Front panel Rear panel U-229 socket for connection of a handset Socket for connection of the transceiver Mode switches

 
Key loading
As the MA-4777 was no controls, other than the two selectors at the front panel, the only way to load a cryptographic key into the device is by means of an external key loader of fill gun, such as the Racal MA-4073 and the MA-4083, both of which are connected to the microphone socket.

The image on the right shows a typical MA-4083 fill gun, which was also used for the MA-4720A tactical VHF/FM radio.

 More information
  
Racal MA-4083C fill gun

 
Zeroise
The cryptographic keys are stored inside the MA-4777 in a volatile static memory (RAM) that is retained by a Lithium backup battery.

In case security is comprimised, the crypto keys can be deleted instantly, by turning and holding both rotary switched fully counter-clockwise to the Z-position. For this you need both hands as the switches are momentary.
  
Mode switches

 
Interior
The MA-4777 is housed in a sturdy slim-line metal enclosure with separate front panel and rear panel assemblies that are watertight. It can be opened by removing the outmost two bolt from the rear panel, after which the rear panel can be separated and disconnected from the rest.
 
Once this is done, the complete interior can be removed by pulling the front panel away from the case. Inside the MA-4777 are two printed circuit boards (PCBs) that are mounted to a die-cast aluminium frame that in turn is attached to the front panel.

The two PCBs are mounted opposite of each other, with a large 34-pin header connecting them. One PCB hold the control circuits whilst the other one is the Crypto PCB. The Crypto PCB can be separated from the rest, by releasing the four bolts in the corners, after which it can be lifted away from the 34-way connector.
  
Crypto unit removed from the PCB

Both PCBs have components at either side. The Control PCB hold a microcontroller with internal firmware. The actual Crypto Logic takes the form of a small sub-assembly that is mounted in a socket on the Crypto Board. It has a number of proprietary OEM chips at both sides and is shown in the image above. This module is also used in secure Cougar (handheld and covert) radios.
 
Rear panel removed Top PCB (crypto board) Bottom PCB (control board) Disassembled unit Crypto board (top) Crypto board (bottom) Control board (top) Control board (bottom)
Crypto board removed Rear view of the front panel Microprocessor and empty EPROM socket Close-up of the backup battery Crypto unit in a socket on the crypto board Modifications in the earlier versions Crypto logic unit (top) Crypto logic unit (bottom)

 
Help required
We are currently looking for the user manual and, if possible, the service manual of the MA-4777, so that we can bring the device to life again. If you have a manual available, or if you have any other kind of information regarding this unit, please contact us.
 
Further information

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Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 21 December 2013 - 13:59 CET
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