Voice scrambler handset
KY-189 was a voice scrambler
for tactical military use, developed by
Napco International in South Hopkins (Minesota, USA) around 1990. 1
The device is housed in a ruggedised military handset and is suitable
for connection to the audio socket of a
military radio sets,
such as the AN/PRC-77,
the AN/VRC-12 the PRC-1077, GRC-160, VRC-64
and many other VHF/UHF narrowband and wideband radios.
One of its first uses was in the Yugoslav Wars (1991-2001)
The KY-189 contains a microprocessor-based
voice scrambling circuit,
with pseudo random rolling code, combined with random timing, audio
frequency shift and synchronisation.
The unit is housed in a small plastic enclosure, very similar to a
standard military handset, but thicker at the microphone end.
On the inner side is a 15-button keypad
and a large red indicator.
Microphone, speaker and Push-To-Talk button (PTT) are at their normal
positions. KY-189 was originally powered by a standard 9V
battery that was fitted in the
large black blob at the bottom.
Later versions could also be powered directly from the radio to which
it was connected , but in most cases the radio had to be modified for
that. The version featured on this page, was adapted for the
military radios (which had to be
modified for the KY-189).
Acording to the manufacturer, the KY-189 offers more than 100 million
user-programmable security codes and the built-in key generator has a
cipher period of 84 x 109 years. Each time the Push-To-Talk (PTT) switch
is pressed, the code changes to a new pseudo-random code.
It also features Automatic Number Identification (ANI),
Status and Location
Report, All Stations Alert Tone, a programmable Time-out Timer and
Selective Call. Each KY-189 has a built-in unique Master Code Key,
used for joint network operation and preventing unauthorised use .
In 1994, KY-189 was in use with US Armed forces, for use with the
and PRC-1077 radios, by the Croatian Army
and by several (undisclosed) government customers .
Although the device provided reasonable security for tactical
applications at the time, the use of a
in general, no matter how complex, should never be considered
secure. With wave-pattern analyzing techniques – often software based –
they can be broken in (near) realtime.
This is a rough estimation, based on the fact that the device
appears first in Jane's Military Communications catalogue of 1994 
and the fact that it was first used in the Yugoslav Wars in 1991 .
The image below shows to position of the controls and features of the KY-189.
The unit has the same shape as a standard military handset, making it very
easy to substiture existing handsets for KY-189 units. The unit is controlled
via the 15-button keypad at the center. At the left is the Push-To-Talk (PTT)
switch. At the right is a metal clip that allows the handset to be affixed
temprarily to, say, the uniform. At the bottom is the coiled cable with a
radio plug at the end.
The large red LED provides visual feedback when in secure or clear mode.
The keypad is used to enter the required encryption key, but can also be used
to send map references, code words and status reports to the base station
silently. Radio checks can be performed without speech .
When the Yugoslav Wars broke out in 1991, the KY-189 was just being
rolled out in the Croatian Army. Approx. 50 units had been distributed
when the hostilities started and it is believed that no further units
were delivered after that .
Although the KY-189 provided reasonable security for tactical communication
at the time, it was known by the Yugoslav Army to be breakable, which is
why the latter swapped most of its
KzU-61 voice scramblers for
digital KzU-63 encryption units.
➤ Yugoslav encryption devices
Getting access to the interior of the KY-189 is rather simple. The large
black 'blob' below the microphone, normally houses a 9V battery. It can
be accessed by removing 4 bolts from the bottom panel. In the version
shown here, the battery compartment is present but unused.
The reason for this is that in this case the KY-189 was powered by the
radio to which it was connected. The battery compartment itself can be
removed by releasing two recessed bolts, after which a
small adapter board is revealed.
The actual voice scrambler is hidden
behind the keypad and can be accessed
by releasing the 6 bolts around the edges of the keypad frame. This reveals
a sandwich of two small PCBs that are connected to the wiring of the handset
via 2 connectors (a 7-pin and a 4-pin one) at the rear.
The PCBs are not bolted or affixed in any way.
The upper board (i.e. the one facing the outside) contains the
actual switches of the keypad
and is slightly larger than the other one.
The two PCBs are held together by means of three inter-board connectors,
and can be separated easily by
pulling them apart.
Although the text has been removed from all ICs, the upper board seems to
contain the digital parts, whilst the other one holds most of the
analogue stuff. The rear board is much thinner and is bended somewhat.
The reason for removing the text from the ICs is arbitrary.
Some manufacturers did this because they didn't want to 'educate' the
competition, but in many cases it is possible to identify the components
simply by looking at the layout of the PCB and the rest of the circuitry.
A truely interested competitor could also x-ray the components and
easily identify them that way.
The KY-189 seems to be designed as a low-cost alternative to the high-end
external voice scramblers that were available at the time, possibly as a
commercial off-the-shelf (COTS) product. It is built from low-cost
commercial-grade components and is housed in a relatively simple enclosure
with no special parts or board retainers. Yet, it complied with the usual
military specifications  and had the advantage of being fully
self-contained and easy to implement.
When looking at the exterior of the KY-189, one can't help but noticing
the striking resemblance to the DSP-9000 that was manufactured by
Technical Communications Corporation (TCC)
in Concord (Massachusetts, USA) around
the same time (1992) . It is housed in a nearly identical case, with the
main visible difference being two extra rows of keys in place of large
Furthermore, the DSP-9000 has a large toggle switch at the right,
to select between secure and clear modes, but apart from that
the housing is nearly identical to the one of the KY-189.
The specifications of the DSP-9000 are also similar to those of he KY-189 ,
the manufacturer of the DSP-9000, is somewhat vague about the
technology that is used.
Whilst their website and brochure suggests that it offers
real encryption, the fact that it performs (proprietary) operations in the audio
time and frequency domain suggests that, no matter how advanced, it is in
fact a voice scrambler.
Although the KY-189 is no longer available from Napco, the DSP-9000 was still
available from TCC in 2022,
as a base station (DSP-9000),
as a handset (DSP-9000 HS)
and as an OEM implant board. According to their website,
the DSP-9000 is interoperable with the HSE-6000 headset .
➤ More about the DSP-9000
The KY-189 has a fixed coiled cable with an audio connector at the end.
The unit is powered by the device to which it is connected, which means
that a suitable voltage must be present on one of the pins of the connector.
The KY-189 was adapted for various radios, simple by suppling it with the
appropriate plug at the end of the coiled cable. The following connections
Most Amerian radios have a 5-pin or 6-pin
for connection of the handset. If the 6-pin variant was used, the radio
could be modified for use with the KY-189. In that case, +12V had to
be supplied to the centre pin (F) .
In all other cases, an internal battery was needed.
The KY-189 was used in combination with various Yugoslav radio sets,
such as the RUP-12
and the RU-2,
both of which featured the same 7-pin audio socket.
As no power supply is normally available on this connector,
the radios had to be modified for this → (+12V on pin 5).
- GND (or not connected)
The KY-189 is compatible with (or could be modified for) many radios, including:
Any links shown in red are currently unavailable.
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© Crypto Museum. Created: Friday 29 May 2015. Last changed: Thursday, 04 August 2022 - 07:53 CET.