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DDR MfS ← Horizont
UHF agent-to-base radio system
GRENZE (English: Border) is the codename of a secret cross-border
agent-to-base radio system,
developed around 1988 by Department 33 of the Technical Operations Division
(OTS/33) of the Ministerium für Staatssicherheit
(MfS, Stasi) — the intelligence service of the former DDR (East-
Germany) — for use by Stasi Department HVA/VIII.
The devices were manufactured at Institut für Nachrichtentechnik (INT) and
Funkwerk Berlin (FWB), both located in East Berlin (DDR) [6].
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GRENZE was intended as a replacement for the ageing
HORIZONT communication system
that had been in service since 1978 and was easy to detect and intercept.
GRENZE uses frequency hopping (FH) as a countermesasure.
The first specifications date back to 1982 [A] and it seems likely that
the development of the devices started in 1985 or 1986.
By November 1988, GRENZE was reportedly 'complete'
although the firmware was probably still under development
at that point.
The first production batch was completed around March 1989 and was
scheduled for deployment in 1990. In November 1989 however, the
Berlin Wall fell, which led to
reunification of Germany in 1990 and eventually
the end of the Cold War.
It is therefore unlikely that the GRENZE system was ever used in practice.
Nevertheless it gives a good insight into the advanced state of technology
in East-Germany and the capabilities of the OTS engineers
at the time of the Wende.
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The image below shows the basic components of the GRENZE communication
system. At the left is a standard
EPSON HX-20 portable computer that is
used as the controller for the TSS-2 transmitter at the centre.
At the right is the receiver, which is shown here without the
controlling computer.
Each of the devices must be powered by an external 12V DC source.
The HX-20 computer is powered by internal batteries that should be
charged with a mains adapter before use, which takes approx. 8 hours.
A full charge of the batteries allows 50 hours of uninterrupted operation.
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The simplest configuration of a GRENZE system is shown in the block
diagram below. At the left is the agent station, which consists of
the TSS-2 (32262) transmitter and an EPSON HX-20 (with appropriate
software), which is used as a control and message device. At the right
is the TSE-2 (32261) receiver, which is connected to a regular
personal computer with suitable software.
Note that it is a one-way data link from the Agent to the Base, running over
a UHF frequency in the 70 cm radio band. This means that it is a line-of-sight
(LOS) system that is suitable for use in urban areas at distances between
4 and 50 km, depending on obstacles like buildings and mountains.
It also means that the Agent does not receive a confirmation of his
transmission. The range of the system could be extended by adding
so-called repeater stations in the transmission path.
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A more complete setup is shown in the block diagram below. It is known
by the Stasi designator Projekt 32922.
At the left is the field station (i.e. the agent side) which is located
outside DDR borders. Frequency hopping data for the
transmitter is provided by the connected controller, or by a
cassette player using audible tones (AFSK).
The transmitter was connected to a directional UHF antenna with circular
polarisation, and transmitted its data at a speed of 38.47 kb/s.
At the right is the base sation, which was internaly known as
Projekt 32922-12. It consists of an 92132-21 antenna (or similar) and
up to three TSE-2 receivers that were controlled by an IBM-compatible
computer (Projekt 32261-43) with suitable software on floppy discs. All units
were powered from the mains, via an uninterrupted power supply unit (UPS)
that could span a power outage of 20 minutes. Each TSE-2 receiver could
handle up to six TSS-2 field stations.
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Receiving station
32261-43
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The diagram below shows the receiving station in more detail. From the antenna,
the signal is amplified in a distribution amplifier, and then applied
to the three TSE-2 receivers. The receivers are controlled via their
serial port (RS232) by a regular MSDOS compatible computer (PC) that also
processes the received data. The PC was initialised with 5¼" or 3½"
floppy discs containing the initial frequency and the frequency hopping
tables (FH), that had been prepared at Base.
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Receiving station 32922-12
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Data received from the field station(s) was processed by the MSDOS PC,
and then delivered to a connected
teleprinter in 5-bit baudot format. It was usually saved to 5-bit perforated
tape, after which it was (manually) sent to Base via a
regular telex subscriber line.
The data was not directly passed to the Base by means of a modem,
although this might have been a later option.
Note that no printer, keyboard and monitor were connected to the PC,
although these peripherals could be connected for maintenance purposes,
for example when installing or updating the software.
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When they were first delivered, the TSE-2 receiver and the
TSS-2 transmitter were each
wrapped in a plastic bag and
stowed in the yellow-brown transit containers shown in the image
on the right.
Each container consists of
two plastic shells that are held together
by a metal bracket at either side, that is fitted to the bottom shell.
The serial number of the unit is printed on a white label at the centre
of the upper shell.
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The TSE-2 receiver is the largest of the two devices.
It is housed in a light grey metal enclosure that measures
88 × 155 × 280 mm and weighs 3526 grams. All connections
are at the side with the black heatsink.
The device was fully controlled by an external MSDOS-compatible
computer, that was connected to its serial port. Currently,
no information about this controlling computer is available.
➤ Look inside the receiver
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Special cables were supplied for connection of the TSS-2 transmitter
to the EPSON HX-20 computer, and for connection of the
TSE-2 receiver to an MSDOS-compatible computer.
Neither of these cables is currently available to us and we are still
trying to work out the required pinout for such cables.
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The TSS-2 transmitter and TSE-2 receiver are extremely
complex devices.
Although we would normally take such devices apart completely to show
their interior, we have decided to only partly disassemble them. The
reason is that the devices are brand new and are still in their
original state. To show all aspects of the devices, we would have to
desolder part of the wiring. Nevertheless, the photographs below
should give a good impression of the build quality of the devices.
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The transmitter is housed in a grey metal enclosure that is open at
one end. The interior is fitted to the black heatsink that also
holds the connections. It is held in place by means of two screws
at the other end of the enclosure. After removing these screws,
the interior can be removed from the case. Some force may be needed
as the rubber gasket behind the heatsink may be binding.
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The receiver is housed in a grey metal enclosure that is open at
one end. The interior is fitted to the black heatsink that also
holds the connections. It is held in place by means of two screws
at the other end of the enclosure. After removing these screws,
the interior can be removed from the case. Some force may be needed
as the rubber gasket behind the heatsink may be binding.
The receiver consists of many different sub-circuits, each of which
is housed in a shielded com–partment. The compartments are assembled
into three planes: one at the top, one at the bottom and one at the
centre. The image above shows how the top and centre planes are hinged,
which allows the interior to be opened like a book. At the front is the
wiring between the three planes.
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The TSS-2 transmitter and TSE-2 receiver in our collection
were both new-old-stock (NOS) when we received them,
packed in sealed plastic bags
and stowed in the original storage containers.
We therefore assume that they are both in working condition and that no
restoration is required.
Ideally, we would like to bring both devices
to life, but for that, full knownledge of the serial control protocols
is needed.
It should be possible though, to extract the control protocol for the
TSS-2 transmitter from the disassembled source code of the
transmitter [H],
whilst we might be able to extract the control protocol of the
TSE-2 receiver
from the available Stasi documents. This is an ongoing process that will
hopefully evolve over time. Any progress will be reported here.
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- Reconstruct TSS-2 control protocol
- Reconstruct TSE-2 control protocol
Work out pinout of TSS-2 serial port - Work out pinout of TSE-2 serial port
- Work out pinout of the 7-pin connector of the TSE-2
- Find connectors for both devices
- Create serial cables for TSS-2 and TS-2
- Create power cables
- Write test software for TSS-2 and TSE-2
- Restore EPSON HX-20 computer
- Port test software to HX-20 computer
- Setup realistic demonstration link
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- Circuit diagrams of the TSE-2 receiver (project 32261)
- Serial cable between TSS-2 and HX-20
- Serial cable between TSE-2 and PC
- 7-pin connector for TSE-2
- LEMO connectors
- Power cables
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The TSS-2 transmitter (32262) has a 4-pin S-series (half-moon) size-0
LEMO socket for connection of the data
input. Two interfaces are available on this connector: (1) serial data from
the HX-20 controller (unmodulated data, RS232C, one way),
and (2) two-tone AFSK data from a tape player (modulated data, one-way).
The latter could be used to read frequency hopping tables that had been
prepared elsewhere, directly from a tape cassette.
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GND - Ground GND - Ground RXD →] Serial input from HX-20 RXA →] Audio input from tape player (AFSK)
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The transmitter is powered by an external 12.5V DC source,
which must be connected to the two pin LEMO connector at the front
panel.
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At the front panel of the receiver (i.e. the side with the large
black heatsink) are three connectors: one for connection of the
antenna, one for the interface to a personal computer (PC),
and one for connector to the power supply unit.
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The receiver has a large 7-pin receptacle for connection of power and
possibly also other signals. The pinout of this connector is currently
unknown.
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The receiver has a 4-pin S-series 0-size LEMO socket on which the
serial RS232 port is available. The pinout of this connector is
currently unknown.
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Device(s) Spy radio system for digital data Purpose UHF line-of-sight (LOS) agent-to-base communication Codename GRENZE Project 32922 Developer MfS OTS/33 User MfS HVA/VIII Classification VVS B 307 Development 1988 Manufacturing 1989 Operational 1990 Country DDR (East-Germany) Predecessor HORIZONT (32900) Frequency 440-465 MHz (frequency hopping) Span 25 MHz Channels 251 Spacing 100 kHz Speed 38.47 KBaud Groups 1 200 (600 max.) Modulation DPSK Dimensions see below Weight see below Quantity 20-50 (est.)
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Each group consists of 5 letters (A-Z) and a space.
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- Frequency hopping
- Differential Phase-Shift Keying (DPSK)
- High data rate burst transmission (38,400 baud)
- Computer controlled Automatic Link Establishment (ALE)
- Simple operation
- Frequency management system
- Low chance of detection
- Low chance of interception
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Device DPSK Receiver Purpose Secret communication (base side) Model TSE-2 Project 32261 Year 1989 Country DDR (East-Germany) Frequency 440-465 MHz (frequency hopping) IF1 76.8 MHz IF2 10.7 MHz Bandwidth 80 kHz @ 6dB Stability 3·10-6 Sensitivity 1µV Interface RS-232C Speed 9600 Baud - 100 m
Power 12V DC Temperature 0°C to 50°C Dimensions 88 × 155 × 280 (HWD) Container ? Weight 3526 g
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Device DPSK Transmitter Purpose Secret communication (agent side) Model TSS-2 Project 32262 Year 1989 Country DDR (East-Germany) Frequency 440-465 MHz (frequency hopping) Output 1.5, 5, 15 W Interface 1 RS-232C (1200 baud) RX only Interface 2 FSK (1200 baud) 1200/1800 Hz Data 11-bit (1 start bit, 8 data bits, 2 stop bits) neg. logic Storage 600 groups (max. 200 used) Cycles 2 Power 12V DC Temperature 0°C to 50°C Dimensions 46 × 90 × 185 mm (HWD) Container 65 × 110 × 204 mm (HWD) Weight 1266 g
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32261 TSE-2 Base receiver 32261-43 Controller for three TSE-2 receivers 32261-100 Test transmitter (uses start channel) 32262 TSS-2 Agent transmitter 32922 Complete GRENZE system (TSE-2/TSS-2) 32922-12 Receiving station 32922-21 Uninterrupted power supply (UPS) 92132-21 Base station antenna
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TSS-2 1289/11 Crypto Museum, Netherlands TSE-2 1389/26 Crypto Museum, Netherlands
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- Aufgabestellung zur Studie TSS 2/TSE 2
Requirements for the feasibility study of the TSS-2 and TSE-2 (German).
VVS-o203 MfS-Nr. B 368/82. Dr. Henkelmann. Berlin, 5 November 1982.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1924. [2]
- Protokoll zur Themenberatung TSS/TSE-2 von 6. 4. 1983
Minutes of meeting at INT Berlin about the development of the TSS-2 and TSE-2 (German).
VVS-o203, MfS-Nr. B 156/83. INT Berlin, 6 April 1983.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1924. [2]
- Forderungen zum K-Pflichtenheft TSS-2/TSE-2
Specification for TSE-2 and TSS-2 an their microprocessor platforms (German).
VVS-o203, MfS-Nr. B 320/84. Dr. Henkelmann, 1984.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1924. [2]
- Bericht zur Erprobung der A3-Muster von TSS-2, TSE-2
Report about early tests with TSS-2 and TSE-2 prototypes (German).
VVS-o203, MfS-Nr. B 81/86, Dr. Henkelmann. OTS/33. Berlin, 20 February 1986.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1925. [2]
- Technische Forderungen zum System 32922-51 Funkleitplatz TSS/TSE
Design for a complete system of receiving, intermediate and base sations (German).
OTS/33. Berlin, 24 October 1988.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1223. [2]
- Aufgabenstellung 32261-43 (Bediengerät System 'Grenze')
Technical requirements for receiver controller 32261-43 (German).
OTS/33, Schiffel, OSL. Berlin, 9 November 1988.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1223. [2]
- Taktisch-Technische Forderungen - Bediengerät für Empfangsstelle 32922-12
Description of receiver communication protocol (German).
OTS/33 Schiffel, Schmidt. HVA VIII Degenhardt. Berlin, September 1989.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1223. [2]
- Prof. Dr. Jochen Jirmann, Der Agentensender VSS B307 der Stasi 1
Disassembly of the internal firmware of the TSS-2 transmitter (German).
29 April 2000. 4 pages.
➤ Assembler listing
- DL3CS, Handwritten technical notes about the TSS-2 transmitter
Rudolf Staritz, Bamberg (Germany),
19-26 December 1999.
- TSS-2 transmitter - wiring diagram
Drawing 1451.004-10001/10003. 4 March 1986 — 7 November 1988.
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The title of this article (VSS B307) refers to the Stasi classification
of the item, not the model number.
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- Detlev Vreisleben, TSS-2 and TSE-2 devices - THANKS !
Crypto Museum, November 2025.
- Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
Federal Commissioner for the Stasi-Records.
- Strategie 2000 - Operative Nachrichtenverbindingstechnik
Descriptions of operational and planned intelligence communication technology (German).
MfS OTS, B 37/88. Berlin, 30 August 1988. Page 3.
- Ordnung Nr. HV A 1/86 für die Arbeit mit operativ-technischen Mitteln
OTM Ordnung. VVS MfS o059-A 35/86. Berlin, 15 October 1986. pp. 30-31.
- Degenhardt (HV A/VIII) an Schmidt (OTS/33), UKW-Verbindungssystem 32900
Letter about planned migration from 32900 (Horizont) to 32922 (Grenze) - (German).
HVA/VIII. Berlin, 29 March 1989. 1 page.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1223. [2]
- Schlüsselliste zum PT WUT, Stand 2/87
Index of projects under development per February 1987 (German).
GVS-o203 MfS-Nr. B 61/87. February 1987.
Bundesarchiv — Stasi-Unterlagen Archiv. Mfs OTS, Nr. 1924. [2]
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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 BStU.
Since June 2021 part of the Bundesarchiv and known as
Stasi-Unterlagen-Archiv.
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