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