French clandestine plug-in transmitter - type 2
EE-2 1 is a miniature clandestine short-wave plug-in transmitter
that 'steals' its power from a valve (tube) socket of a contemporary broadcast
receiver, developed around 1954 by or for the French intelligence service
in Berlin (Germany) — the DR/SR. 2
It was the successor to the EE-1 and was used into the 1960s
for agent-to-centre communication across the
in Cold War East-Germany .
It comprises a single valve oscillator, of which two versions are known.
The device measures 223 x 103 x 34 mm and weights just 530 grams.
Unlike its predecessor – the EE-1 – it does not have a built-in morse key.
Instead, a regular morse key must be connected to the banana sockets at
the right hand side of the device.
The other banana sockets are used for the power supply, which is taken
from the socket of the audio frequency (AF) valve of a regular broadcast
receiver of the era, using the supplied power cable. At the end of the
cable is a plug which can be fitted to the socket of the
receiver's AF valve, commonly a 9-pin EL84. 3
According to surviving documents of the former East-German MfS
(Stasi) , EE-2 devices were thought to have been developed in 1954
and were confiscated regularly between 1956 and 1957. They were found
with a morse slide pad –
like the one found with a BCRA transmitter – instead of a regular
morse key. From 1957 onwards, the morse slide pad was replaced by a
wind-up tape player
that acted as a burst transmitter
(see below) .
It is unknown how many EE-2 units were manufactured, but judging from the
professional build style, it was factory produced in series.
As the official designator of this transmitter is currently unknown,
we have nicknamed it EE-2, which is short for Émetteur Enfichable
type 2 (plug-in transmitter type 2).
During the Cold War,
DR/SR was the French intelligence service in Berlin.
It was part of the Sûreté National (SN) and was responsible for army, air force,
political and economic espionage against East Germany and the MfS (Stasi).
It equipped its agents with motor cycles and clandestine radios .
Cables for other valve types have been spotted as well, such as for P-type
sockets (see below).
PLEASE HELP —
Crypto Museum are still looking for additional information about this
transmitter. Please help us to expand this page by providing information
about the development of this device. Where and when was it designed, and what
was the official designator? We would also like to hear stories from people
who have worked with this device. If you have any information,
please contact us
The image below shows what a complete setup might have looked like.
The transmitter takes its power from a domestic broadcast receiver of the era,
and is connected to the socket of the EL84 valve in the receiver's AF stage
via a 3-wire cable with a noval plug at one end.
To avoid mistakes, coloured banana plugs are used, which should match
the coloured dots at the top surface.
For high-speed transmissions
in morse code, either a morse slide pad was provided
or a tape-based burst encoder.
The frequency is determined by one
of 15 crystals in the 4-10 MHz range.
Antenna and counterpoise (ground) should be connected to the
transmitter's front panel. The wires for this were
usually supplied on a pertinax (paxolin) card. The ground wire has a crocodile
clip at the end, which allows it to be connected to the metal pipes of
the water supply or heating.
Note that the text on the iron body of the transmitter
and on the front panel, is engraved rather than
screen printed. Due to rust, the engravings may have deteriorated somewhat.
At least two versions of this transmitter are known, which we will call
Mark I and Mark II:
- Mark I
This is the simplest version of the transmitter, of which the
is presented below. It is believed that this is the earliest
version of the device. The transmitter featured here is of this type.
- Mark II
This version is cosmetically identical to the Mark I, but is internally
somewhat different. Although it is very similar to the Mark I, there are
various improvements to the circuit, probably to make the transmitter
more stable. It is believed that this is a later version. Photographs
of this version can be found in Louis Meulstee's Wireless for the Warrior .
The transmitter is the heart of the clandestine station. It is housed in
metal enclosure that measures 223 × 103 × 34 mm and weights 530 grams.
the enclosure consists of a frame, attached to the front panel, and a
removable shell. At the right side are banana sockets for connection
of the power supply and a morse key. The sockets for connection of an
antenna and a suitable counterpoise are at the front panel.
➤ Look inside the transmitter
For quick transmission of morse numbers, whithout knowledge of
this small contact pad was issued, It consists of six slots
with intermittendly coded contacts, and a slide contact. By moving the slide
contact through one of the slots, the corresponding number is sent.
The slide pad shown here is very similar to the one issued with the EE-2,
and was found with a French BCRA transmitter.
➤ More information
Morse burst encoder
Around 1957 the morse slide pad was replaced by the tape player
shown in the image on the right. It allowed a pre-recorded message to
be sent as a 'burst' in just a few seconds. It not only reduced mistakes,
but also the 'on-air' time, thereby minimising the chance of being captured by means of
Radio Direction Finding (RDF).
The device shown here was captured by the Stasi in the former DDR
➤ Other burst encoders
Power cable for EL84 socket
Power for the transmitter was usually 'borrowed' from a regular
broadcast receiver. In most cases, a cable was supplied that could
be fitted to the 9-pin socket of the EL84 valve that was present
in the audio frequency (AF) stage of the receiver.
Cables for this socket type were found with the EE-2 transmitters
that were confiscated in the DDR in the late 1950s and early
1960s. The image on the right shows a functional reproduction of the cable
and the plug.
➤ Cable wiring for EL84 socket
The transmitter featured on this page, was found in 2022 with
the short power cable shown in the image on the right.
It has three colour-coded banana plugs at one end (red, green
and black), and a P-type plug-and-socket at the other end.
It is uncertain whether this was an originally issued cable or a homemade
add-on by a previous owner, but it allows power to be 'borrowed' from
any receiver that has valves with P-type sockets, such as the EL3, EL6 and EF6.
➤ Cable wiring for P-type socket
At the front panel of the transmitter are two banana sockets:
an isolated one for connection of a wire antenna and a non-isolated one for a
suitable counterpoise (ground). The wire antenna should be long enough to allow
the transmitter to be tuned effectively. In most cases a 20 metre wire will be
The counterpoise could be formed by a similar long wire, but could also be
obtained from existing grounded grids, such as the water supply or heating
Each agent was given a transmission schedule that listed the times and
frequencies for each day of the month. The agent used this schedule when
sending information to the Centre.
The schedule also listed the daily times and frequencies of the broadcasts
of the Centre. A complete transmission schedule was obtained by the Stasi
in the East-Germany in 1961, on double agent DAHLIE .
➤ Description of the schedule
➤ Transcribed copy
The French plug-in transmitter was issued to agents (civilians) in the DDR
(East-Germany) who were spying for the French. Both the EE-2 and its
predecessor, the EE-1, were confiscated on several occasions.
In at least one case in 1961, an EE-2 was obtained by the Sasi, complete with
the tape-based high speed burst transmitter shown in the image below.
It replaced the manual morse slide pad .
The set was obtained through double agent DAHLIE (Wolfgang Herrschaft),
who was recruited by French intelligence, but was in reality a secret
employee (GM) of the Stasi.
The photograph above was extracted from a
Stasi file of September 1961 .
It shows a white 3-wire cable with three banana plugs at one end, and
a 9-pin noval plug at the other. It mates with the socket of an EL84 valve
in the receiver.
A photograph of the EE-2 with the slide pad, and another one of a third
variant concealed as a camera (EE-3), can be found in
another Stasi file .
➤ Read the full Stasi file
The burst encoder (also known as burst transmitter or burst keyer)
is about the same size as the transmitter itself, but thicker. It contains two
spools with a metal tape that is driven by a spring-loaded mechanism.
The mechanism can be wound up by means of a key, much like a clock .
The message is recorded on the tape by means of nail polish in
the form of narrow lines, wide lines, narrow spaces and wide spaces, similar
(but not identical) to morse code.
For this purpose, 10 templates are provided that represent the numbers 0-9.
Once the message is complete, the spools are installed in the playback
mechanism and the wound-up spring is released. It is likely that the
tape is sensed electrically, assuming that the applied nail polish acts as an
The result is a high-speed pattern of short and long beeps and spaces that
is broadcast by the transmitter on a frequency in the short wave band.
At the Centre it is first recorded and then played back at lower speed,
so that it could be transcribed.
It is likely that the latter was done with the help of an undulator
or an automated device that could recognise the patterns.
Apart from a transmitter and a morse code device, each agent received a set of
15 different quarz crystals for frequencies in the 4 to 10 MHz range.
The agent also received a schedule that defined the hour, minute and frequency
for transmission on a given day. It is likely that this schedule was different
for each agent. Below is the transmission schedule that landed in the hands of
the Stasi in 1961, through double agent 'DAHLIE' —
the cover name of Wolfgang Herrschaft (see above) .
➤ Original transmission schedule
The agent would listen to messages from the Centre (German: Zentrale) each
morning at 08:05 or evening at 20:05 at one of the frequencies listed in the
bottom right corner of the schedule above (6.500-6.750 MHz). Messages
addressed to the agent were preceeded by his station number: 32.
The messages from the Centre were transmitted either in
morse code or as spoken words by a French
Numbers Station. They were usually encrypted with a
one-time pad (OTP) that was unique for each agent.
Once the agent had taken down the message, it was deciphered with the OTP
and then converted from numbers to letters, using a predetermined scheme.
The corresponding page of the OTP was used only once and was destroyed
immediately after use.
If the agent wanted to send a message to the Centre, he picked the
two-letter combination from the schedule for the given day in the given month.
For example: for the 31st of July, he gets the combination
h G'. The two letters are used as an index into the two columns
at the far right of the schedule:
ZEIT (time) and FREQUENZ (frequency).
The lowercase letter '
h' yields the time for the transmission: 15:57, whilst
the uppercase letter '
G' defines the frequency: 5.414 MHz.
In the transmission, the agent would identify himself with his station
The message itself consisted of numbers only. In most cases the text was
first converted from letters to numbers using a fixed scheme, and then
encrypted by means of a one-time pad (OTP). At the Centre,
a copy of the OTP was used to decipher the message. The corresponding
page of the OTP was used only once and was destroyed immediately after use.
The EE-2 transmitter is basically a single-penthode Miller oscillator,
built around an American 6AQ5 tube with a crystal – resonating in parallel
mode – connected between the g1 and ground. At least two versions
of the transmitter circuit exist, as the one in our collection differs from
the one shown in Chapter 80
of Louis Meulstee's book Wireless for the
Warrior, Volume, Supplement .
Below is the circuit diagram of the transmitter in our collection,
which we have named Mark I.
We assume this design to be first one. Apparently there were some issues
with the stability of the circuit, as the version shown in the forementioned
book  has two additional RFCs (L3, L4), one additional capacitor
(C5), and one additional inductor (L5) in series with coupling capacitor
C2. The additional components are shown below in red.
We have named this version Mark II.
The transmitter is very service friendly. The interior can be accessed
simply by holding the two knobs at the front panel and
sliding off the case shell towards the rear.
This reveals the interior as shown in the
image above. The only active part is the 6AQ5 valve, which can
be swapped in seconds should this be necessary. All other parts are
passive (resistors, capacitors and coils).
The device featured here, was found with a
General Electric 6AQ5 valve
with a production date of 2-52 (week 2 of 1952).
It is likely that this is the original valve
that was issued with the device.
The device was found in the state that is visible above and in the images
below. After dusting off the front panel, the interior was thoroughly inspected
for faillures. When no issues were found, a 7.015 MHz crystal was fitted, along
with a suitable antenna and counterpoise, after which a 6.3V/250V power source
It worked straight away and after tuning the front panel controls,
it produced a nice and stable morse tone when operating an external morse key.
As no morse key or morse slide pad was found with the device, we decided to
test it with the slide pad of the earlier BCRA transmitter, which
is very similar. For this purpose, a
yellow/blue cable was made to connect
the slide pad to the yellow and blue sockets of the EE-2 transmitter.
As the power cable for connection to the socket of an EL84 valve was also
missing, we decided to create a
functional reproduction cable with red, green
and black banana plugs to connect it to the red, green and black sockets of
the device, using a modified valve extender 1 as a plug.
It is important to note that regular banana plugs cannot be used, as the five
sockets at the right side of the device are spaced too close. It is necessary
to find regular 4 mm banana plugs with a narrow grip, such as the ones shown
in the images. Such plugs are also visible in the Stasi file .
To allow the transmitter to be connected to a regular power supply unit –
for demonstration and test purposes – an extra cable with a noval
socket and three banana plugs was added as well.
A valve extender, or Noval Socket Saver, is used by HiFi enthusiasts
for saving the existing noval sockets of an audio amplifier. It is placed
between the valve and the existing socket.
At the right side of the transmitter are five sockets for connection of the
power supply and the morse key. These sockets accept regular 4 mm banana plugs,
but only with a narrow insulation cap, as the space between the sockets is
insufficient for regular caps. To avoid mistakes, the sockets are coded with
coloured dots on the top surface of the transmitter,
Black● 0V (GND)
Blue● Key (GND)
6AQ5 is an American valve (tube) that was originally intended for application
as a 12W audio frequency (AF) amplifier and later also in the vertical
deflection of a television set. In the French transmitter however, it is used
as an oscillator/PA for the 4 to 10 MHz range.
➤ 6AQ5 datasheet
Below is the pinout of the EL84 valve. This valve is not present in the
transmitter but in the broadcast receiver that was used as a power supply.
It was commonly used in the output stage of the receiver's AF amplifier.
It requires a 9-pin B9A Noval socket.
The layout is as seen from the bottom of the valve (i.e. the solder side of
the noval socket in the receiver).
- not connected
not connectedk, g3
- not connected
- not connected
Below is the layout of the power cable that was found with
the transmitter freatured here in December 2022. It consists of
a socket and plug, and is installed between the valve and the socket.
It is currently unknown for what type of valve and/or receiver it was
intended. The layout is as seen from the bottom of the valve (i.e. the solder
side of the socket in the receiver).
- not connected
- 0V (black)
- 6.3V (green)
- not connected
- not connected
- not connected
- +250V (red)
- not connected
CustomerDRS-SR (French intelligence in Berlin)
Power6.3V, +250V, Ground 1
CableWired for EL84 valve in domestic receiver
Dimensions223 × 103 × 34 mm
Weight530 g 2
Taken from AF socket of contemporary receiver.
Mark I version.
The transmitter was usually supplied with a set of 15 crystals. Depending
on the current transmission schedule, the agent would install one of these
crystals. The following crystals were confiscated by the Stasi of the
former DDR :
- 4.182 MHz
- 4.392 MHz
- 4.802 MHz
- 5.070 MHz
- 5.228 MHz
- 5.328 MHz
- 5.454 MHz
- 5.533 MHz
- 5.742 MHz
- 5.912 MHz
- 6.129 MHz
- 6.312 MHz
- 6.408 MHz
- 6.505 MHz
- 6.924 MHz
Surviving EE-2 transmitters
Mark ICrypto Museum, Netherlands 1
Mark IIDHM, Germany 2
Mark IIPrivate collector, France
Previously held in the collection of Edmond Codechèvre (France).
Formerly held in the Traditionskabinett of the Stasi (MfS).
- Louis Meulstee, Plug-in transmitter French (2)
Wireless for the Warrior, Volume 4, Clandestine Radio, Supplement.
September 2015. Chapter 80.
- Detlev Vreisleben, Information about French Plug-in Transmitter Type 2
- Notes in former MfS Traditionskabinett (internal museum)
Photograph kindly provided by Detlev Vreisleben .
- Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
Federal Commissioner for the Stasi-Records.
- MfS II/3, Merkblatt GM 'Fallstein'
Description of confiscated French plug-in transmitter and burst encoder.
BStU, MfS-HA II, Nr. 41276. Berlin, 8 September 1961. 2
- MfS, ... vom französischen Geheimdienst an Spione in der DDR übergebene Funkgeräte
Equipment handed out by French intelligence to spies in the DDR (German).
BStU, MfS. VVS JHS oOC1 - 70/88, page 163. 2
- Paul Maddrell, Exploiting and Securing the Open Border in Berlin:
the Western Secret Services, the Stasi and the Second Berlin Crisis, 1958-1961.
Woodrow Wilson International Center for Scholars. February 2009. Page 19.
- Philip Parker, The Cold War Spy Pocket Manual
ISBN 978-1-910860-02-1. UK, 8 October 2015. pp. 139-140.
- MfS II, Photographs of confiscated Western equipment 2
BStU, MfS-HA II, Nr. 41369. Undated.
Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes
der ehemaligen Deutschen Demokratischen Republik
Federal Commissioner for the Records of the
State Security Service
of the former German Democratic Republic
officially abbreviated BStU.
Document from BStU archives , kindly provided by Detlev Vreisleben .
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