DEVELOPMENT OF AUDIO-SURVEILLANCE EQUIPMENT AT HOHENSCHOENHAUSEN

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A031900150001-1
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 13
• Document Creation Date: December 22, 2016
• Document Release Date: March 29, 2010
• Sequence Number: 1
• Publication Date: December 21, 1956
• Content Type: REPORT

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~. . r. =10219911808 L
This material contains information affecting the National Defense of the United States within the meaning of the Espionage Laws, Title
18, U.S.C. Secs. 793 and 794, the transmission or revelation of which in any manner to an unauthorized person is prohibited by law.
3ECRET/IIO CRT1
COUNTRY Last Germany
DATE OF
INFO.
Development of t''tudio-Zurveillance
Equipment at Iiohenschoenhausen
NO. PAGES 7
REQUIREMENT
NO.
21 December 1956
PLACE
ACQUIRED
1. The Last German Ministry for State security (:linisterium fuer Staatssicherheit
TdfJ) utilized the services of prisoners at the prison camp of the SSD in
IIohenschocnhausen to design and modify monitoring devices for audio-surveillance.
The prisoners engaged in this work were known as the High Frequency Group.
2. tathouf;h some prisoners claimed that Soviets had formerly visited the carp on
frequent occasions, none wore observed during the. 1953-1956 period. The
rumor that the camp was a "Russian Institute" appeared to be unfounded, oven
though 00 percent of the miniature amplifiers produced were allegedly for the
Soviets.
3. From June 1953 to iluguot 1956, the following devices of Uc tern origin wore
delivered to the HiGh i,'rcquency Group:
c. Ten to 20 ,t:?bster wire recorders;
d. Several hundred wire recorders these had a
plafinf time of one and one r - u wore probably used to monitor
telephone conversations;
lltransistorizedll pocket receivers (type unknown);
Hearing aids ma afa:z cturcd
Almost eve of 0
Gorman.
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aids. Copies of the publication were also received. A 25X1
prisoner was required to explain the purpose of the various articles and devices
mentioned in the periodical and, on occasion, to translate the articles into
Those devices were delivered in an assembled state. As far as is known, they
had not been altered b- the 33D, with the possible exception of the hearing
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40
iniature Transmitter
a. Prior to June 1953, Ernst Krause, formerly of Fuzkwerk Dresden, had
completed the development of an ultra short-wave FIJI miniature
transmitter
with a frequency range of 70 to 80 megacycles and an effective range of
150 to 500 meters. The transmitter had been deveianni at the request of
th
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was in w_
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Group arge assembling the devices; all construction components
were of Western origin. Two types of transmitters were made: one line-
powered which could operate as long as the mechanism was in order, and one
battery-powered which could operate for approximately four days.
b. The line-powered transmitter had the following major components:
1 high frequency condenser microphone
1 subminiature tube, exact type unknown
1 ultra short-wave coil
1 rectifier
1 line transformer, type 24 42 (former general German designation)
The microphone, built by Krause, was probably designed initially tr the
Soviets as they had been working on a microphone at the prison at an
earlier date. It was approximately the size of an American 25 cent coin
and had a frequency range of 100 to 10,000 cycles. The microphone consisted
of aluminum foil with a eountereleetrode milled in the following designs
The amount of power conoumod 1r the transmitter was so slight that it
would not register on in ordinary Watt motor. These transmitters were
allegedly to be built into the wall under switohboxes, May were glindri-
sal in shape with a diameter of approximately 100 millimeters and a loom
of approximately 150 millimeters, The sensitivity was allegedly so great
that the tranoiittere could be affixed to the opposite side of the veil of
the room to be monitoreds
as The battard-powered tram" vmor had the same characteristics and oeostsvetdon
elements as the line-powered typo oxqopt that the line transformer and
rectifier wore reply e'l IV a leortrix 'anode battery of 30 V and a Psrbris
filament of 105 V. Both batteries were of Western origin. The bstteryi.
powered transmitters wore installed in cigarette packs, in large fo mtaim
ppns, and in pencil cases. Krause in still working on this transmitter.
00 is attempting to ace a 5 V battery and two transistors. In addition
to Krause, three mechanios also wort?od on the transmitter. Thos@ voce
Prod Wieseke (formerly of Punkwerhh Kadeberg), Horst IteAffe, ~d wern~sr
Dahlberg. Guenther aobol, an engineer now at had Olankonbur~,
worked on the transmitter at one time and may knew the o ate=drawing for
the devise. Dobel also built broadcast r ceivers, using transist?
woo and tr emitter/receivera to be attached to a web-bolt. The
tranamitt@rfreoeivers were allegedly for use of the infantry in intersom.
munioations.
Reaeiyin Unite far l Baia t re ~i a niit a
a. The prison had We Rhode and tiohwars ..ueivers which were probably used to
pick up the miniature transmitter broadcasts, One had a froqusnoy range
from ultra short wave to medium wavoi theseoond from Medium to loess were.
The receivers were intended for concurrent operation.
*be Prior to 1963, the ddD staff had attempted to oanotruct small rescuers
- fer the transmitter. Krause had waited on several of thaw bat the dosips
SKQET/NOPONN
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were not satisfactory. Finally, he took parts from a Rhode and Schwarz
standard receiver and attempted to miniaturize the design for the 70 to
80 megacycle rage. Krause's technical ability was doubtful and although
he designed at least seven types of receivers and produced approximately
10 units of each type, even the seventh modification was unsatisfactory.
This was used, however, as no other was available. Practically all
necessary types of equipment were available for this research; almost all
were of Rhode and Schwarz design.
6. ionitorinrr Devices Evolved from Iiearintr Aid
a. The first "transistorized" Beoton hearing aids arrived at the camp in :larch
or April 1955. They came in two sizes: large with white cases, and small
with blach cases. Both types were equipped with four trazi istbrs. At
first, the hearing aids wore modified only by detaching the microphone and
inserting a microphone cat lo between the microphone and the amplifier. The
hearing aids were then installed directly as monitoring devices. Prior
.to 1953, Beoton devices using subminiature tubes instead of transistors
had been treated similarly.
b. Z me I Device
1) The original transistors in the hearing; aids apparently were not
powerful enough for the use intended by the XD. "':ortly after the
hearing aids wore received, work began on the designing of an improved
monitoring device using other types of transistors. A device was
designed from a circuit dia&ram, probably drawn on the basis of the
Beoton devices by S3D officers in charge of the group. The prisoners
believed that the 33D personnel carefully screened Western publications
and used ideas found in them to modify the circuits of the devices.
Dy Juno or July 1955, the basic design for the first device was
completed. This was referred to as Type I by the prisoners, although
this was probably not the type designation assigned by the SSD. The
device was a 4-stago transistor amplifier with a dynamic microphone
in which the original transistors were replaced by the more powerful
models. Dy the end of 1955, seven or eight variations of the design
had been carried out in order to improve the device mechanically and
electronically. The work was of a trial-and-error nature and inmates
of the prison did as little as possible to further the work.
2) In Feb 1 6 lar e auantities O -
C 70- 00 71 ~t. trans-
istors, re
delivery to cat%p. They arrived in their original boxes evA&
oontcl-ring 100 transistors. They may have been purchased
as the transistors were available there. Last German trans.
istors made at Toltow .,l Dr. Falter (fnu) had been tried but they
wore too large and not reliable. Russian transistors had also been
trxa4 but tests indicated they were not reliable and the voltage
requirements (50 V) were too high for use in miniature work.
3) After delivery of the transistors, construction of Type I
device was begun. About 150 were produced but not all were completely
equipped with transistors and microphones. When now, many of the
Type I devices may not be ready for operation because of lack of
secondary components. Also, some of the prisoners working on the
project have boon released from the camp.
4) Models of the device had been tested. The testing; took place in
another department and no details are available. The technical data
for Type I are contained in the explanation of the circuit diagram
shown in Attachment A.
a. ,II (see Attachment B) was developed in a manner similar to that of
Type I, from various handwritten circuit diagrams which had to be
calculated and refined. The design for Type II was completed by hatch
1956, models were produced and tested, and the prisoners wore put to work
constructing the devices. Approximately 150 Typo II devices were con-
structed but, like Type I. all may not be finished and ready for operation.
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14.
9.
8. Erasure of Recording tare
One of the tasks at the camp was the construction of a device for rapid
erasure of recording wire; this device was doveloped an the basis of a
suggestion made ter RTI Nuremberg for erasing magnetic to . The erestwe
effected tat fading a ading alternating field. The irductanoe (I1 Or 12) snd
capacitance (C) of a tank circuit were selected so that damped osoillatiaes
resulted. (See Attachment D). Two coils were arranged one above'the vld ;
to form a pocket which held the wire spool. The wire could Ithen be a,-
in a few seconds.
9.
a. In January 1956, a prisoner was asked to develop a monitoring device trlii0b
could record conversation over the noise of a radio. No literature on
the subject was offered and the prisoner refused to undertake the prajesU
b. A 3-transistor amplifier had been built for insertion into a standard
telephone condenser with connections as indicated in Attpahments E tr
This unit would operate whoa the telephone was not in uss. gpproodisa~
15 of the devices were built.
. III (see Attachment C) was a 3-stage transistor_am.ifier
represented a further development carried out on the bas" CV4VM I-
II. An =determined number of OC 65 and OC 66 transistors arrived ad;.
prison in April or May 1956, and tr that time the theoreiticat dses~n
Type III had been completed. Only one model of Type III had been ado
l+pr August 1956.
At no time did the SSD personnel make any direct statement concerning the
success or failure of the operation of the devices, whether they had been
put into operations, or for what purposes they were used, Any of the three
typea can be tied into a telephone line to pick up conversations in the
room, using the power from the telephone line to operate' the device. 40,
telephone line can be tapped at any point along its course and the 3
conversation recorded on the machines. Testing the telephone line ioW
detect the tap for monitoring the device but not the tie+-in of the 4isito
to the line.
ARUM
P-55 Ilinifons with 4-hour spools were used as recorders. Flay-back'
made in conjunction with a 10 W amplifier and a loudspeaker. A secret
project was underway at the camp to develop a method for, remote eontrcd
of a Minifon but no details of the project are known.
I-anifon recorders had been modified to operate under water when attaeia'
to the hulls of ships, The microphone would allegedly be concealed on
board, The number of recorders modified for this purpose is wikna m4
One of the prisoners had been asked to produce a miniature recorder buh.F:y
when he requostod equipment and supplies for this work he was refused s11d
no worl: was accociplirhed.
transistors, rectt.fiers, and diodes at VEB Work ,ier Bauelement der
Nact:richtentechnik (WAN) Carl von Oesietzky in Berl in-Teltoww.
4. Dr. Mathias Falter was previoue2.y reported as chief of de7,elopment!6
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Attacbment
EXPLAIIATION OF BASIC CIRCUIT DIAGRAM OF 44TAGE TRANSISTOR AIIPLIF ILR WITH
DYNAIIIC MICROPHOTIE AND TELEPHOIJ ; LINE (TYPE I)
Rev to Diagram
1. Dynamic microphone with alternating current resistance of 200 Ohms and 0.1
millivolt per microbar.
2. Shielded microphone cable (nay be up to 50 meters in length).
3, Amplifying system with four stages.
4. Valvo transistor OC 70.
5. Volvo transistor OC 71.
6. Valvo transistor OC 71.
7. Valve transistor OC 72.
S. Telephone line with alternating current resistance of 600 Ohms.
9. Power supply.
10. Connections for recording output of amplifier.
Technical Data
Frequency range: 150 to 9000 cycles 12 decibels.
External voltage interval: 55 decibels.
Effective output: +1 neper at 600 Ohms.
Noise factors 3 percent.
Dimensions of the amplifying devices approximately 100 x 50 x 20 mm,
SECHL-71110F0RN
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EXPLANATION OF BASIC CIRCUIT DIAGRAM OF 4-STAGE TRANSISTOR AMPLIFIER WITH
CRYSTAL MICROPHONE AND TLLI! PHONE LINE (TYPE II)
to Di"ran
1. C tal microphone with alternating current resistance of 500
2. Shielded microphone cable with maximum length of 10 meters.
Amplifying system with four stages. Stages 1 and 2 are the receiver and
stages 3 and 4 are the transmitter. The input Impedance is approximately
500 kilo Ohms. The output impedance is approximately 600 Ohms.
4?
Valvo transistor OC 70.
5.
Valvo transistor OC 70.
60
Valvo transistor OC 71.
7.
Volvo transistor OC 72.
8.
Telephone line with an alternating current resistance of 600 Ohms.
9.
Power supply.
10.
Recording device.
loc ctn. Data
Frequency rango: 150 to 9000 cycles _ 2 decibels.
External voltage interval: 50 decibels.
Microphone: has a super elevation of approximately 30 decibels at between
1000 and 7000 cycles.
Effective output: +1 neper at 600 Ohms.
Noise factor: not known.
Dimensions of amplifying device: 100 x 50 x 20 mm.
" GRE"OFr
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EXPLANATION OF BASIC CIRJIT DIAM M W 3-STAGE TRANSISTOR ATG?Lfl'IER WITH
DUANIC M t0PII0NE #UD T=P1I01NE LINE (TAPE In)
Sear to Dias
1.
Dynamic microphone with alternating current resistance of 200.1000 Ohms
and 0.1 millivolt per microbar.
2.
Shielded microphone cable= mwdmum length 100 meters.
Amplifier: 'Stages 1 and 3 are the transmitter circuit.
is approximately 1 kilo Ohm.
Valvo transistor OC 65.
The input impedaaoe
5.
Valvo transistor OC 66.
6.
Volvo transistor OC 66.
7.
Telephone line with alternating current resistance at 600 Cbms.
8.
Power supply.
9.
Recording device.
Frequency range: 150 to 8000 cycles _ 2 decibels.
Effective outputs 0 nepers at 600 Ohms.
Noise factor: not known.
rxternal voltage interval: not known.
Dimensions: 60 x 40 x 20 mm.
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