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Opto Voice ZEISS Stasi JO-4.02 → ← JO-4
The device consists of three basic elements: a triple mirror unit,
a voice amplifier (transmitter) and a infrared receiver. It is called
a passive device, as it does not actively radiate infrared light itself.
Instead, it has to be illuminated by an infrared beam from the outside —
typically a JO-4.02 or JO-4.03
that could be placed up to 1 km away,
as long as it was in the line-of-sight (LOS).
The core of the device is the triple-mirror, which comprises a prism
and a membrane-mirror, as shown in the image on the right.
The membrane is excited by the audio (speech) of the operator.
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The triple-mirror system is housed in a
trapezoidal enclosure with
an infrared (IR) filter at the front.
In the simplest configuration, the triple mirror is used as a
stand-alone device, without any additional active components.
The performance can be enhanced by using a
Sennheiser MM-23 microphone
and an audio amplifier, to assist the membrane-mirror.
If two-way communication was required, an infrared receiver
could be added to the setup. The device was supplied in the
most complete configuration, so that it
could be used for all three possible configurations [A].
Due to the wide-angle nature of the device, it should not be placed
behind regular window glass (reflection) or above a heater (turbulence),
and the active area (i.e. the input port) should not be obscured in any way.
The device was developed at
Carl Zeiss Jena (CZJ) in Jena
(DDR) between 1976 and 1979.
Production started around 1983 and lasted until at least 1989, just before
the fall of the Berlin Wall.
A spin-off from the JO-4.01 development, is the Rostock infrared bug.
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JO-4.01 consists of three basic elements: a triple mirror, an audio amplifier
(transmitter) and an infrared receiver. Depending on the application, one,
two or all three of these items are used. The device can be used in three
different configurations that are further explained below:
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In this configuration, only the triple mirror unit is used. It consists of
a triangular glass body with one fixed mirror, and a reflecting membrane that
acts as the second mirror. The two mirrors are placed at a 90° angle, in
such a way that they reflect an incoming (unmodulated) infrared beam.
At the right is the opposite station, which in most cases was a
JO-4.02 (Große Dahme). In this configuration the JO-4.02
acts as an activation device. It illuminates the triple mirror with
an unmodulated infrared beam. The membrane-mirror is excited by the
operator's voice and modulates the reflected infrared beam, which is then
picked up by the receiver of the JO-4.02.
This is the only purely passive mode. It requires a person to speak
close to the membrane.
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The membrane in the above configuration can be assisted by adding an
miniature lapel microphone,
an audio amplifier and a miniature speaker
(bascially an earpiece). By placing the speaker in the vicinity of the
membrane-mirror, the amplified audio excites the membrane.
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JO-4.01 in assisted (simplex) mode
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This mode is known as the assisted or active mode. It is a one-way
system that is activated (illuminated) by an unmodulated infrared beam
from the JO-4.02 at the other end. Although the
amplifier is dubbed transmitter, the device only transmits when
it is actively being illuminated.
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In the most complete configuration, an infrared receiver is added to
the setup. It is mounted close to the triple mirror, so that it 'sees'
part of the the infrared beam from the base station. It enables full
duplex communication. If necessary, the receiver could also be detached
and used elsewhere.
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JO-4.01 in full-duplex mode
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In this mode, the illumination beam from the base station – which activates
the transmitter – can be modulated with the speech from the operator at the
base station. Note however, that in that case, the reflected beam contains
the voice data from both ends of the link.
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Type Acoustic-optical modulator [3] Purpose Covert cross-border agent communication User MfS (Stasi) Manufacturer Carl Zeiss Jena Angle (2ω) 20° Bandwidth 300 Hz - 4 kHz Active area 48 x 22 mm (i.e. the size of the IR-filter) Dimensions 63 x 42 x 40 mm Temperature -20 to +45°C
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Type AF audio amplifier (electro-acoustic amplifier) Power 2 to 3V DC Current < 1 mA Max. level 80dB Impedance 200 - 2000 Ω (microphone) Bandwidth 300 Hz - 3 kHz Power 2 to 3V DC Current < 1 mA Batteries 2 x LR-6 Alkaline (sufficient for 2 months) Dimensions 104 x 63 x 40 mm Temperature -20 to +45°C
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Type Infrared receiver Power 2 to 3V DC Current < 1.5 mA Angle (2ω) 12° Active area 10 mm Ø Impedance 600 - 1000 Ω (earpiece) Dimensions 104 x 40 x 23 mm Temperature -20 to +45°C
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- Acoustic-optical modulator
- Electro-acoustic amplifier (transmitter)
- Infrared receiver
- Earpiece
- Lapel microphone Sennheiser MM-23
- IR notch filter
- External power cable (short and long)
- Receiver power cable
- 2 dummy batteries
- Set of screws
- Screwdriver
- Lint-free cloth
- Leather storage case
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- JO-4.01 - Development planning 1
MfS/CZJ, 1976, 1977, 1978.
- JO-4.01 - Development phase A1, Final Report (German) 1
Bestätigungsbeleg zum Entscheidungsprotokoll der Verteidigung: A1.
CZJ, 28 October 1977 (signed 28 November 1977).
- JO-4.01 - Development phase A4, Template (German) 1
CZJ, 27 August 1979.
- JO-4.01 - Development phase A4, Progress Report (German) 1
CZJ, 30 August 1979.
- JO-4.01 - Development pahse A4, Test Results (German) 1
CZJ, 12 September 1979.
- JO-4.01 - Development phase A4, Final Report (German) 1
CZJ, 25 September 1979.
- Test and adjustment aids for JO-4.01 (German) 1
Justier- und Prüfmittel. CZJ, May 1982.
- JO-4.01 test result 1983, 1985 1
CZJ, Handwritten documents (German).
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Document obtained from BStU [2] and kindly supplied
by Detlev Vreisleben [1].
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Document obtained from BStU [2] and kindly supplied
by Detlev Vreisleben [1].
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Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes
der ehemaligen Deutschen Demokratischen Republik
(DDR) —
Federal Commissioner for the Records of the
State Security Service
of the former German Democratic Republic (GDR) —
officially abbreviated to BStU.
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Document obtained from BStU [2] and kindly supplied
by Detlev Vreisleben [1].
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© Crypto Museum. Created: Thursday 16 December 2021. Last changed: Tuesday, 14 March 2023 - 09:49 CET.
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![Prism and membrane mirror used at the core of the triple-mirror. Photograph by Detlev Vreisleben [1].](img/303752/001/full.jpg)
![Complete JO-4.01 system with triple-mirror, transmission amplifier, receiver, microphone and earpiece. Photograph by Detlev Vreisleben [1].](img/303752/002/thumbnail.jpg "image # 303752/002")
![Triple-mirror (passive unit). Photograph by Detlev Vreisleben [1].](img/303752/000/thumbnail.jpg "image # 303752/000")
![Prism and membrane mirror used at the core of the triple-mirror. Photograph by Detlev Vreisleben [1].](img/303752/001/thumbnail.jpg "image # 303752/001")
![Complete JO-4.01 system with triple-mirror, transmission amplifier, receiver, microphone and earpiece. Photograph by Detlev Vreisleben [1].](img/303752/002/full.jpg)
![Triple-mirror (passive unit). Photograph by Detlev Vreisleben [1].](img/303752/000/full.jpg)
