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SBO Cold War NL Philips NSF
A full set consists of three same-size units:
a transmitter,
a receiver
and a power supply unit,
each housed in a black metal container with a lid
that is held in place by a leather strap. A fourth container
holds the spare parts and accessories.
The crystal-operated transmitter is suitable for
CW (morse) in
the 2.5-9 MHz frequency range, and delivers an output power of
4 to 4.5 Watts. It is operated either with the
built-in morse key, or
an external one.
The receiver
has a a VFO, and is adjustable from
3.2 to 7.2 MHz. It is suitable for A3 signals (AM, phone)
and A1 (CW, telegraphy).
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The three units are interconnected by means of short cables that are
fixed to one of the units.
The set is powered from the 110/220V AC mains, or from a 6V DC
source, such as a car battery.
The ZO-47 was used by the
Dutch stay-behind organisation O&I
for the transmission of text-based messages — containing
only the 26 letters of the Latin alphabet — that were encrypted with a
so-called One-Time Pad (OTP).
When used correctly, the OTP cipher
is unbreakable.
The first 100 sets were delivered to O&I early in 1948. A second
batch of the slightly improved ZO-47/01 was delivered a few years later.
The ZO-47 is probably the only Dutch spy radio set ever developed.
In the late 1950s, it was succeeded by American
and later also by German radio sets.
The existence of the ZO-47 remained unknown to the
public until two complete sets were found in a
'forgotten cache' 3 in Utrecht (Netherlands) in 1992.
After the incident, all remaining sets were collected and destroyed.
The set shown here is one of the very few surviving ones. 4
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At the time, NSF was a wholly-owned Philips subsidary.
➤ More
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Other spy radio sets were developed by Philips subsidary MBLE.
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A cache is a secret storage place of weapons, ammunition and (radio)
equipment that can be accessed by its controllers in case of an
emergency. Caches are often related to clandestine activities.
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Only two complete sets are known to have survived.
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Crypto Museum would like to thank the Dutch Army's
Signals Service Historical Collection
for supplying the documentation of the ZO-47 and the ZO-47/01, and allowing
us to make them available on this web page.
We are also indebted to Wim Kramer — who had been able to investigate a ZO-47
from a forgotten cache find in 1992 —
for sharing his experiences, publications
and photographs, and for allowing us to reproduce them here [2][3][4].
The ZO-47 consists of
four equally sized metal boxes
with a lid on top. The lid was held in place by a
leather strap that ran through a 'gutter' at the
centre of the lid, and had a so-called
Click button at the end. The four
boxes were finished with black wrinkle paint and contained a
power supply unit (PSU),
transmitter (TX),
receiver (RX)
and a collection of accessories
and spare parts.
The diagram above shows the various features of the complete ZO-47 radio set.
At the right is the Power Supply Unit (PSU) which should be connected either
to the AC mains (127 or 230V) or a 6V DC source. The PSU is connected to
the transmitter by means of a short power cable and the transmitter in turn
powers the receiver via another short cable, which is visible at the lower
left.
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- ZO-47
This is the original version that was developed by Philips in 1947.
It is built around Philips Rimlock 41 valves (tubes) and has the text on
its front panels printed in orange. All plugs (including the
AC and DC power connectors) have their cable entry at the top.
It came with a
small brown 8-page illustrated booklet
that has the model number Z.O. 47
imprinted at the front cover [A].
The radio sets that were found in a forgotten cache in Utrecht
in 1992, and that were destroyed before the investigation was concluded,
were of this type [2].
- ZO-47/01
This is an improved version of the above one, built with Rimlock 42
valves. It was released several years later and
has some mechanical and electrical improvements. Furthermore the
text on the front panels is printed in white and a much more
elaborate manual with full circuit diagrams was supplied.
The set featured on this page, is of this type.
More...
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The initial version of the radio set was known as ZO-47 or ZO-47/00
and was developed in 1947. The first batch of 100 units was delivered
early in 1948. It is believed that there are no surviving examples of
this version, although two complete sets were found in a
forgotten cache in 1992. 1
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The image on the right shows the condition of the set when it was
discovered in 1992 [4]. As it had been hidden under the floor of a basement
for several years, it was badly corroded and not operational. Nevertheless,
many of its features and electronic circuits were still recognizable.
The set is built with Philips EAF41 and ECH41 Rimlock valves, with
exception of the EBL21 valve in the PA of the transmitter and an
AZ41 dual rectifier valve in the PSU. Many of the passive components
in the transmitter and the receiver are from standard (civil) production [2].
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The LT and HT voltages are delivered by the PSU via a short fixed
cables with a straight 3-pin Philips connector at the end.
These connectors were also used on professional audio equipment of the era.
The set was supplied with
a pair of American R-30-U military headphones that had been manufactured by
Woolcot in 1945, along with a collection of other accessories.
Surprisingly, no external morse key was found with the radio set,
suggesting that the internal key was used by default.
The set came with a
simple 8-page instruction booklet with
funny illustrations [A].
➤ More about the forgotten cache
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Both sets were destroyed in 1992, after the investigations had hit a dead end,
along with a large number of other surplus radio sets that had been used
by the clandestine network.
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Several years after the first 100 radio sets of the above type had
been delivered to the secret organisation, another batch was ordered
from Philips. As newer valves and even semiconductors had meanwhile
become available, it was decided to include some improvements in the design.
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Instead of the EAF41/ECH41 valves, the newer EAF42/ECH42 were used.
Furthermore, the AZ41 rectifier valve inside the PSU was replaced by a Selenium
variant that was manufactured by AEG.
The vibrator unit and the transmitter's EBL21 PA tube
had survived from the original design.
The basic circuit design had remained unaltered.
Other improvements of the internals are the use of professional components
instead of civil parts and better mounting of the neon lamp inside the
transmitter. Though small, such improvements generally enhance the
equipment's reliablilty.
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The text on the front panels of this variant was screen printed in white,
whereas it had been orange on the initial version. Another change to the
exterior was the use of right angle plugs for the power distribution,
as a result of which the overall height of the set was reduced when it
was in full operation. This would have been more convient when using the
set from inside a suitcase.
The ZO-47/01 came with a well-written
63-page manual
with full operating instructions, circuit descriptions, alignment
procedures and full circuit diagrams [B]. It is currently unknown
when this variant was released, but it is likely that this was several
years after the introduction
of the initial version. Judging from the manufacturing codes this might
have been between 1951 and 1954.
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During WWII, The Netherlands had two independent intelligence agencies,
both of which operated from England. The first one was
Bureau Inlichtingen or BI (Intelligence Bureau).
It was controlled by the Dutch Government in
exile (London) and was similar in nature to the
British MI-6.
The BI was tasked
with gathering military, political and economic intelligence, mainly on
Dutch territory.
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The other special agency was
Bureau Bijzondere Opdrachten or BBO (Special Operations Bureau).
It operated directly under (and was largely controlled by) the British
Special Operations Executive (SOE).
The main tasks
of the BBO were to setup a resistance organisation,
and to carry out sabotage actions in occupied Netherlands.
The BI was led by
Colonel J. Somer who –
before the war – had already started
the formation of a secret section of the Dutch General Staff under the name
GS III C. During a war, the main tasks of GS III C would be active intelligence
gathering (espionage) and stay-behind. By 1939, Somer had succeeded in setting
up GS III C, but it was too late to be of much use during the war.
Once the war was over, Somer rejuventated his GS III C section, albeit in
a less ambitious form than he had anticipated. His GS-III-C section
was actually the post-war variant of the wartime BI.
For the stay-behind activities
of his section, Somer needed communication equipment.
After using a variety of Army Surplus (mainly from Belgian stores),
he managed to secure a budget of NLG 20,000 (EUR 9100) for the development
of the first and only Dutch spy radio set: ZO-47.
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The order for the development was given by Somer in 1946.
Development by Philips/NSF
took most of 1947 and by the end of that year the radio was
ready for its first field test. In early 1948, the first batch of 100 units
was delivered. By that time however, Somer had already left GS-III-C
to become head of intelligence in the Dutch Indies.
He was succeeded by J.J.L. baron van Lynden.
➤ History of the Dutch stay-behind organisation O&I
➤ More about Jan Marginus Somer
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The explosive case of Parkstraat 3
In the first week of August 1992, the police in Utrecht (Netherlands)
got a phone call from the owner of the house at Parkstraat 3.
He intended to sell the house, but wanted the police to run an investigation
first, as there was a persistent rumour that the were explosives hidden
inside it.
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The police took the matter seriously and, using a metal detector,
discovered some metal packages hidden under the floor of the basement.
As the packages appeared to be badly corroded, they called in the national
bomb squad (EOD), 2 who took over the job of digging out the packages.
The EOD found six 9 mm FN-Browning pistols, a Welrod suppressed pistol,
a box with a number of hand granades, ammunition, detonators and finally
two complete radio sets with spares and accessories, spread over several
metal boxes. It were thought to be leftovers from World War II.
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It was rumoured that the house had been used by the
German Sicherheitsdienst (SD)
during the war, and that they had probably hidden the weapons there.
But when the EOD closely examined the weapons, they came to the conclusion
that they were British-made and not German. From that moment on, the police
assumed that the weapons were used by the resistance and had been confiscated
by the SD during the war.
But when the investigation showed that the SD had used the house at number 2
— opposite the current one — this theory had to be abandonned as well.
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In the meantime, the arrival of the bomb squad had attracted the
attention of the public and the Dutch national press.
As a result, the discovery appeared in the
headlines of several newspapers
the next day — 6 August 1992 —
and even in the 8 o'clock news on national TV (NOS Journaal).
On 11 August, the news was picked up by Wim Kramer, a freelance author for the
Dutch Radio Amateur Magazine (RAM), who immediately contacted the Utrecht
Police with the request to be allowed access to the discovered equipment.
And against his expectation, he was admitted.
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The equipment had been stored temporarily in the workshop of the Utrecht
Police, where their weapons expert had already succeeded in partly restoring
some of the guns. Resistance experts were still discussing the wartime role
of the resistance with members of the investigation team.
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When Kramer arrived, the radio sets and their accessories were
scattered all over the floor
of the workshop as shown in the first photograph of this
section. Kramer had expected to find war time
British spy radio sets,
such as the large B2 suitcase radio
or the smaller A3,
but to his surprise the sets were completely unknown to him.
After recognising the typical 3-pin Philips power connectors and checking
the numbers on the spare valves, he arrived at the conclusion that
this was not a wartime British radio set, but far more likely a post-war
device built by Philips.
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Kramer was allowed to further investigate the equipment. After cleaning the
units as good as possible, he wrote an excellent
'educated guess' of how the
equipment might have worked, and was allowed to publish a
detailed description
in RAM of October 1992 [2] in the hope that a member of the public would
recognise the equipment and come forward with an explanation.
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In response to the article, the author received about 20 phone calls,
most of which hinted to a secret hitherto unknown organisation nicknamed
GLADIO, 3 but neither of them had recognised the set or was able to
provide further details.
The involvement of a secret organisation could explain the presence of
the eight codebooks that had been found with the radios: four blue ones and four
with a red linen cover. The blue books were labelled
DECODEREN (decoding)
whilst the reds books were titled CODEREN (coding).
Each of the books contained a set of numbered pages.
The books had been damaged considerably by moist,
but fortunately they were still readable.
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Each page contained 100 five-letter groups
that were separated by pre-perforated
lines, much like a sheet with stamps. The 'stamps' were organised as 10 rows
by 10 columns, and each one could be torn from the page individually.
It was clear that these books were one time pads.
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Despite the efforts of the investigators — aided by Wim Kramer, members of the
public and the press — the results of the investigation were inconclusive
and the spooky case hit a dead end.
As the equipment was about 45 years old,
it was assumed that the people responsible for it had long since died.
And to make matters worse: the state prosecutor had decided 4 that all
weapons and equipment that had been discovered, were to be destroyed.
Despite several requests from museums and private collectors, that is
exactly what happened: all evidence was destroyed...
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Or was it? When Wim Kramer visited the
Dutch Signal Corps Museum five years
later, in 1997, he stumbled upon a ZO-47 set in near-mint condition in
one of the display cases. Apparently a few years earlier the officer responsible
for the destruction of the equipment, had exhibited a great sense of history.
On his way to the blast furnices in IJmuiden (Netherlands), where the sets were
to be incinerated, he dropped off several unique radio sets that had once belonged
to O&I.
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Story by Wim Kramer, published in Radio Amateur Magazine (RAM) of October
1992 (Dutch) [2]. Translated and partly reproduced here by kind permission
and cooperation from the author.
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EOD = Explosieven Opruimingsdienst (Dutch national bomb squad).
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In the preceeding years, several (inter)national incidents had raised public
awareness of a secret stay-behind organisation in The Netherlands,
which was confirmed in 1990 by (then) Prime Minister Ruud Lubbers.
Shortly after the Parkstraat discovery in 1992,
Lubbers officially dismantled the organisation.
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It is still a mystery why the state prosecutor (Dutch: Officier van
Justitie) wanted the equipment to be destroyed, but it is possible,
if not likely, that he had received instructions from someone 'higher up'.
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In most situations it was recommended to power the ZO-47 directly
from the mains. As the radio was intended for use by a stay-behind
organisation (SBO), this means that it had to be suitable for all
mains networks in The Netherlands [7].
This was not straigthforward however, as the country had a wild
variety of mains voltages (127V and 220V) and even a mixture of
AC and DC.
Today all mains power networks in the world are AC, but
at the time the ZO-47 was issued (1948), some parts of The
Netherlands still had a DC network. 1
As the PSU of the ZO-47 is not suitable for DC mains networks,
it had to be powered from a 6V DC car battery in these areas [A]:
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- Ameland (Nes and Hollum),
- Arnhem (partly)
- Boxtel
- Groningen (city, partly)
- Rotterdam (partly),
- Schiermonnikoog
- Utrecht (city, partly)
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AC = Alternating Current, DC = Direct current.
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In places with a DC mains voltage, but also in areas without a mains
network (fields, woods, etc.), the ZO-47 could be powered from a 6V
DC source, such as the battery of a car. In some cases, a suitable
battery was supplied with the set, so that it could be used in
virtually any situation.
When connecting a battery to the ZO-47, the AC mains cable has to
be removed as it otherwise interferes with the 6V rail. The polarity
of the 6V DC connection is not crytical and may be reversed, as the
internal vibrator pack converts it to an AC voltage anyway.
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The Power Supply Unit (PSU) is the heaviest of the three modules.
It can be powered either by the AC mains or by a 6V DC source, such as the
battery of a car, and converts it into 6V AC for the filaments and 300V DC
for the transmitter, which in turn converts it into 250V for the receiver.
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When powered from the AC mains, the correct input voltage (126V or 230V) has
to be selected, by placing the mains fuse in the correct fuse holder
under the rengtangular 'bulge'
at the front edge. Spare fuses are also stored there.
The output of the PSU is available from a short fixed cable with a right angle
3-pole female plug at the end. On the initial version of the ZO-47, a straight
plug was used for this purpose, but this increased the total height of the radio
set when all cables were connected, and was probably a cause for intermittent
(cable) contact problems.
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Inside the PSU is a conventional transformer with two primary windings
(to allow for 110V and 20V AC mains voltages), plus a so-called
synchronous vibrator pack, that converted the 6V DC (battery)
voltage into an AC voltage that could be 'stepped-up' with the transformer.
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The crystal can be used at its fundamental frequency (i.e. the frequency
that is printed on its body) or at the 2nd harmonic. In the latter case
there will be a power output penalty, as the frequency doubler causes some loss.
It is therefore advised to use the fundamental frequency.
At the top left is the band selector. It selects the correct tap on the
transmitter's tuning coil and should be set as close to the desired frequency
as possible. With the correct crystal installed, the antenna tuning knob
at the bottom right should tuned for maximum output of the PA stage.
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This is done with help of the tuning indicator (lamp) at the top right.
The knobs should be adjusted for maximum light. Once the optimum is found,
the ring of the indicator lamp can be turned to reduce the amount of
emitted light. The transmitter can be used in always-on mode (Z),
or in break-in mode (BI). The latter requires separate RX and TX
antennas to be installed.
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The transmitter is only suitable for the sending CW-signals
(morse). This can
be done either with the built in morse key, or with an
external one that is
connected to the socket marked SLEUTEL (English: key) to the right of the crystal socket.
An external morse key was not supplied with the set, so we have to assume that
the operator was required to bring his own preferred key, or that the built-in was
used by default. Despite its rather high position, the quality of the internal
key is actually quite good. It can be adjusted with the
two screws at the radio's front edge.
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A major issue when transmitting CW, is the appearance of so-called
key clicks, a clicking sound that can be heard in regular broadcast
receivers in the vicinity of the transmitter, when the user presses down the
morse key. Such clicks are unwanted as they might reveal the presence of
the clandestine radio station. The transmitter of the ZO-47 contains a filter
to avoids such clicks.
Note that when using an external morse key, the pins of its banana plugs
should be no longer than 10 mm. When longer (i.e. regular) banana plugs
are used, they will engage an
integrated switch
that permanently enables
the oscillator. According to the manual [B] this was reserved for
special applications, which probably means that it was provided for
connection of a burst keyer. 1
This feature was only present on the ZO-47/01 and was
omitted from
the initial ZO-47 of 1948.
The transmitter is powered by the PSU
by connecting the short fixed cable of the
PSU to the 3-pin socket of the transmitter. It provides the transmitter with
6V AC (LT) for the filaments, and 300V DC (HT) for the anodes.
The transmitter converts the anode voltage to 250V,
which is available on the fixed cable at the bottom left.
This cable should be connected to the receiver's power socket.
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A burst keyer
is a device that allows a pre-recorded message to be sent
in morse code
at high speed, in order to evade
interception
and radio direction finding.
Also known as burst transmitter or burst encoder.
When sending at high speed it is generally necessary to turn
the transmitter's oscillator ON permamently.
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The receiver is the final unit in the power chain. It receives its
6V AC (LT) and 250V DC (HT) power lines from the fixed cable of the
transmitter.
A wire antenna of approx 6 metres long (shorter than
the 20 m TX antenna) and a similar counterpoise,
should be sufficient for a good reception.
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The antenna and counterpoise are connected at the top left.
A high-impedant or low-impedant pair of headphones should be connected
to the banana terminals at the bottom left. A suitable
pair of headphones
was supplied with the radio.
The receiver can be tuned freely over the entire frequency range
between 3.2 and 7.2 MHz in a single band. It has a frequency tuning window
with two scales: one that has been calibrated in MHz, and a linear scale
from 0 to 100. The latter can be used to accurately mark the position
of a station, so that it can be found back more easily.
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The receiver is suitable for the reception of Amplitude Modulated
(AM, or A3) signals, as well as CW (A1, or morse).
In the latter case, the BFO has to be
turned ON by turning the BFO knob clockwise. The knob can then be used to
adjust the signal ± 2 KHz, for optimum tone quality.
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The radio set came with a variety of accessories and spare parts,
such as power cables,
antenna wires,
crystals,
spare fuses and
spare valves, that were neatly packed inside a metal container.
The container is simular to the other units, and has a removable lid
that is held in place by a leather strap. Inside the lid is a
storage bay for up to 20 crystals,
plus an artificial antenna.
Spare light bulbs and fuses are packed in a small carton box that
is also stowed in the container.
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The ZO-47 could also be powered by a 6V DC source, such as the battery
of a car, 1 in which case the AC power cable had to be removed and the
DC power cable shown in the image on the right had to be installed
in the 7-pin DC socket.
Like the AC connector, this 7-pin plug was briefly manufactured by
Nederlandse Seintoestellen Fabriek (NSF)
and is extremely rare. 2
➤ DC connector pinout
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At the time of the ZO-47, most civil cars had a 6V battery.
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This connector was missing from the ZO-47 set in our colection, but
could be reproduced from donated spare parts of an old NSF-device
in the collection of Arthur Bauer.
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A metal spool with 20 metres of isolated copper wire, was supplied
as the transmit antenna. The wire has a banana plug at the end, that
mates with the transmitter's antenna socket.
A separate 6-metre piece of isolated copper wire was used as the
receive antenna. It should be connected to the antenna socket on the
receiver.
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For a proper operation of the transmitter, the ground socket should
be connected to ground (earth). This is especially the case when using a
¼λ antenna, instead of the proposed ½λ one.
A suitable ground wire is supplied with the set. It consists of a short
3-metre wire with a banana plug at one end, and a clamp at the other one.
The clamp should be fitted to an appropriate ground connection, such
as the water supply.
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No external key was found with the set featured on this page, but
it is unlikely that the internal key
was used at all times, as its position
is rather unpractical. It is possible that the operator was given the
option to bring his or her own key.
In most cases, this would have been a British, American or German leftover
from WWII, for example the German Ta.P. Wehrmacht key that is shown in
the image on the right. It's connector directly fits the SLEUTEL socket to
the right of the crystal. Note however that the pins of the connector should
not be longer than 10 mm.
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The ZO-47 is suitable for both high-impedant (2000 Ω × 2) and
low-impedant (150 Ω) headphones, by connecting them to the
appropriate termials at the bottom left of the front panel.
The standard headset (shown here) consists
of two R-30-F earpieces, made in 1945 by Woolcot (USA). They are
held together by a canvas head strap
(missing here), allowing it to be worn under a helmet.
Alternatively, the
R-30-U in-ear variant
with metal bracket could be used.
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The crystal socket on the transmitter accepts two types of crystals,
both of which were common at the time. The socket accepts crystals with
a pin distance of 12.5 mm and a thickness of 2.5 mm, but also the
larger variant with 3 mm thick pins and a pin-distance of 19 mm.
Although it is possible to double the crystal frequency,
it is recommended to use crystals of 2.5 - 9 MHz at their fundamental
frequency. Up to 20 crystals can be
stowed in the metal lid of the
accessory container.
➤ More about crystal shapes
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Tuning the transmitter for maximum output whilst the
wire antenna is connected, raises the chance of detection and
discovery by means of
Radio Direction Finding (RDF), leading to the
operator's arrest and endangering the mission.
To minimise the time on-air, the dummy-load, or artificial antenna,
shown in the image on the right was used during the tuning stage.
Once the transmitter was properly tuned, the real antenna was reconnected.
The dummy load is stowed
inside the top lid
of the accessory container.
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A small carton box with spare fuses and light bulbs was supplied
with the set. It was usually stowed inside the metal accessory container.
Some of the larger lamps are wrapped in paper, whilst other are fitted
in the cut-outs of a small wooden block. For an overview of the items
in the carton box, please refer to this list.
➤ List of items
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Each set also came with a selection of tools – such as screwdrivers
and pliers – divided over two small canvas tool bags. As both these
bags and the tools are missing from the ZO-47 in our collection,
we are unable to show a picture.
➤ List of items
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All three modules are housed in a nearly identical enclosure.
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The Power Supply Unit (PSU) can be opened by removing three bolts
from the bottom of the case and sliding off the case shell (which can be
rather difficult as it is a tight fit).
The image on the right shows the interior of the PSU. About half the space
is taken by the large transformer. The two cylinders at the center are the
vibrator, which is used when powering the PSU from a 6V source,
and a Selenium rectifier. In the ZO-47/01, the Selenium cell replaces the
AZ41 rectifier valve of the original ZO-47.
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The design of the transmitter is pretty straightforward. It consists
of an oscillator, built around an EAF42 (or EAF41 in the earlier model),
and a power amplifier (PA) with an EBL21.
When sending in morse (CW) using the built-in key
or an external one,
an internal filtering circuit avoids key-clicks.
The anode voltage (HT) of both the oscillator and the PA are switched ON
and OFF with the morse key, which limits the maximum speed. When using
a burst encoder, the oscillator was turned ON permanently by a switch in
the key socket.
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The receiver can be opened by removing a single bolt
from the bottom, plus two at the corners of the control
panel. It is the most complicated of the three units and is built
around five valves.
The circuit comprises a single super heterodyne receiver, consisting
of an RF amplifier, a variable frequency oscillator (VFO), mixer,
IF amplifier, BFO and AF amplifier. All valves are EAF42, with
the exception of the mixer, for which an ECH42 is used.
The IF frequency is at 475 kHz.
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The diagram below shows the pinout of the 3-pin Philips power input
socket on the receiver. It needs four wires: the three pins, plus the
shield which acts as the ground (0V).
The pinout is shown when looking into the
socket from the controls. Note the position of the reference mark.
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- Sidetone
- +250V DC (HT)
- 6V AC (LT) for filaments
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The diagram below shows the pinout of the 3-pin Philips power input
socket on the transmitter. It needs three wires: two of the pins,
plus the shield which acts as the ground (0V).
The pinout is shown when looking into the
socket from the controls. Note the position of the reference mark.
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- not connected
- +300V DC (HT)
- 6V AC (LT) for filaments
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The diagram below shows the pinout of the battery power socket.
Note that the position of the notch on the plug should be at the
bottom. Inside the plug there should be three loop wires as shown
below. Pin 5 is unused. The 6V battery voltage should be supplied
to two thicker pins (1 and 3). The polarity of the 6V DC voltage
is not critical and may therefore be reversed.
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- 0V
- Loop with 7
- +6V
- +6V
- not connected
- 0V
- Loop with 2
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The diagram below shows the pinout of the mains power socket on
the PSU, when looking into the socket. The AC mains is connected
to the two thick pins that are the furthest apart. The position of
the notch on the plug should be at the top. Note that a loop wire
has to be present between pins 2 and 3. It provides the necessary
internal connection for the 6V rail.
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- 127 - 220V AC
- Loop with 3
- Loop with 2
- 127 - 220V AC
- not connected
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Device Spy radio set Purpose Clandestine stay-behind communication Manufacturer Philips-NSF User Stay-behind, O&I AC power 127 or 220V, 50 Hz DC power 6V battery (external) TX frequency 2.5 - 9 MHz (crystal operated) RF power 4 to 4.5 Watts RX Frequency 3.2 - 7.2 MHz IF Frequency 475 kHz BFO range ± 2 kHz Weight 10 kg
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- Dummy load
- Neon bulb for antenna tuning
- Wire antenna, approx. 30 meter with banana plug (transmitter)
- Wire antenna, approx. 6 meter with banana plug (receiver)
- Spool for antenna wire
- Ground wire with plug and clamp
- Frame for holding 20 crystals
- Full circuit diagram (printed on metal)
- Mains power cord
- Battery power cord
- Low-impedant headphones
- High-impedant headphones
- Carton box with spares
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- 3 x fuse 0.5A 1
- 3 x fuse 0.8A 1
- 3 x fuse 10A 1
- 2 x lamp 12V/5W Philips 10/12 A7 - 12914 T, for dummy load 1
- 4 x lamp for antenna current indicator 1
- 1 x neon lamp for sidetone 1
- Vibrator unit
- Set spare valves (1 x EBL21, 1 x ECH42, 4 x EAF42)
- Bag with banana plugs (3 x black, 3 x red)
- Banana interconnector
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- Tube puller
- Small screwdriver 1
- Small pliers 1
- Ferret drill 1
- Side cutter 1
- Pipe wrench 1
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Divided over two tool bags.
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Crypto Museum are still looking for the following items:
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- Spare valves: 1 x EBL21, 1 x ECH42, 4 x EAF42
- Spare vibrator Philips 6V type 7948
- 4 x white egg-isolator
- Tools with bags
- Canvas strap for headphones
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Derived from date codes in the circuit diagrams.
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- Herman Schoemaker, Een geheime organisatie in beeld
De Nederlandse stay-behind-organisatie, geheim, onafhankelijk en zelfstandig?
The Dutch stay-behind organisation, secret, independent and autonomous?
(Dutch).
Thesis under supervision of Prof. Dr. B.G.J. de Graaff,
Utrecht University. 7 June 2013.
- Wim Kramer, Mysterie in Utrecht
RAM Magazine 136, Oktober 1992. pp. 17-19. 1
- Wim Kramer, Mysterie in Utrecht na jaren opgelost
RAM Magazine 191, Oktober 1997. pp. 32-35. 1
- Wim Kramer, Photographs of the equipment found at Parkstraat 3
Personal correspondence. Received April 2015. 1
- Historische Collectie Verbindingsdienst, ZO-47/01 radio set
Signal Corps Historical Collection (Netherlands).
Retrieved February 2009 and May 2016.
- De Telegraaf, Dansen op explosieven in Parkstraat
Dancing on explosives at Parkstraat (Dutch).
Newspaper, 6 August 1992. Retrieved April 2015.
- Wikipedia (Dutch), Lichtnet
Retrieved June 2016.
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Reproduced here by kind permission of the author Wim Kramer.
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Any links shown in red are currently unavailable.
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© Crypto Museum. Created: Friday 15 July 2016. Last changed: Monday, 12 February 2024 - 21:15 CET.
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![Wim Kramer at work in the workshop of the Utrecht Police in August 1992 [4]](img/wk_work1_large.jpg)
![Wim Kramer at work in the workshop of the Utrecht Police in August 1992 [4]](img/wk_work1_thumb.jpg "image # wk_work1_large.jpg")
