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Racal Voice
The unit is smaller than any of its predecessors and measures just
16 x 6 x 21 cm. It is inserted between the handset and the transceiver
and allows voice signals to be encrypted using a combination of
Time Element scrambling and Frequency Processing, in half-duplex [1].
The MA-4470 employs a novel continuous synchronisation system that
allows late-entry and that is virtually transparent to the
user when switching the transmission direction of the half-duplex link.
The unit can be powered by the host radio set, or by an external
power supply unit.
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All controls and connection are at the front panel.
At the left are the sockets for the handset (or headset) and
the transceiver. To the right of the sockets is a 4-character
LED display and some LED indicators that are used for user feedback.
The right half of the front panel is taken by the 25-button rubber
keypad, which is used for switching between clear and secure,
entering the base key, using the fill-gun, selection of the current
key and ereasure of the key(s).
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The cryptographic keys are 80-bits long and can be entered
by typing 20 hexadecimal digits on the keypad.
Alternatively, the keys can be entered using a suitable
key-fill device (fill-gun), such as the MA-4255 Master Programmer
or the MA-4459 Slave keygun [1].
The image on the right shows the
Racal MA-4083 fill-gun that looks similar
to the MA-4459 slave keygun that is used with the MA-4470.
The MA-4255 Master Programmer is housed in the same case as the
MA-4225 portable encryptor.
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The front panel of the unit acts as a backplane for the four PCBs.
Each board uses a 64-way DIN connector for connection to the backplane.
A small metal bracked, that is usually stored in between the PCBs,
can be used to pull-out the individual boards.
The image on the right shows the processor board, which is the 2nd board
from the top, half-way out of the case. The metal bracket is shown here
in front of the PCB. Detailed pictures of each board can be found below.
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Principle Time Element scrambling and Frequency processing Keystream Non-linear keystream generator External key 8·1031 Internal key 26 bits Base key 80 bits per key (from fill-gun) or 20 hex digits (via keyboard) Stored keys 16 base keys + 1 guard key (selectable via keyboard) Key period 1024 bits Message key 24 bits Modulation FSK in frequency processed channel at 48 baud Cycle time > 90 days Battery life 5 years Response 400Hz - 2400Hz Bandwidth 400Hz - 2700Hz Audio delay 495 ms Input level TX: 0dB, 1mV - 50mV, RX: 70mV - 3.5V Output level Adjustable to match input level (max. 1.5W into 8 Ω) Power supply 12V - 32V DC, 120 - 300mA Temperature -20°C to +65°C (operation), -40°C to +70°C (storage)
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MA-4255 Master Programmer MA-4459 Slave Keygun MA-4220 NiCd Battery for Master Programmer MA-4234 Battery Charger (230V AC) for Master Programmer MA-4454 Battery Charger (115V AC) for Master Programmer
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Leaflet kindly supplied by Paul Ratcliffe, January 2013.
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© Crypto Museum. Created: Thursday 26 August 2010. Last changed: Tuesday, 10 August 2021 - 16:29 CET.
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