Secret Communications 3

Status 4


Status: 25 October 2019



2 (25 October 2019)


Please notice that: during the Secret Communications 3 exposition, we are hosting materials owned by the "Cryptomuseum in Eindhoven".

Incorrectly noticed on the web: Our premises is legally not connected with the of Eindhoven.

Albeit, that the proprietors of the Cryptomuseum - are both members of the board of our Foundation:

Stg. C.D.V. & T.



Time has come, that we should dedicate attention toward our future exposition displays; because - approximately a single month has left. 


I suppose, that we have moved already >> 1000 kg devices and artefacts, as to make sufficient space for the new exhibits;

neglecting the weight of the artefacts brought-in by the Cryptomuseum, from Eindhoven.


In the background it is visible, that some of our regular exhibits will remain on their place.



A pre-view of our exhibition preparations

Viewing in front: a collection of significant  "Philips/Usfa" products.



Viewing some of the new exhibits on display in our rear exhibition room


Quite much is dealt with, such as: "Bugs" (miniature hidden-microphone devices)  and the test gear; as well as detecting the existence- and direction of such means.

Shown are quite old types, though, also rather "state-of-the-art" samples.


Inside the Perspex cube, we look at a Russian broad-band set, designed for broad-spectrum detections.

For each range a different cassette has to be adapted. On top of the cube we look at "underwear";  which were carrying hidden antennae covered under a coat or that means. 



We have to apologise for the current disorder

But we are in a preliminary state of building up the exhibition.

It is even not unlikely, that some ultimately will be put on display entirely different.



Our aim always is: to display photos on our website - in such a way: that also those utilising a low-resolution access (for example using a 'smartphone' or an old type computer), that they will get illustrations and pictures just fitting onto someone's low-resolution screens , too

HTML is adapting always automatically the horizontal text versus display-resolution.


Please, notice again, that we still are in a processes of transition.


Which Raymond, Deo volente, will demonstrate:



No comments

The free corner in front is scheduled for the ominous Dutch 'Pocket Telex' collection; of the late 1980s



Please notice, that transition: also implies, that we have to facilitate power means; in this case for the two German telephone scramblers, type GL IIIb (in wartime days: driven from an 2 V accumulator (filament) and an anode battery) 

Technically, my aim is: to use the German NA 6 power supply, but not converting anything inside.

The filament output, isn't controlled (regulated) at its output voltage - but by means of its output current. (employing a hydrogen controlled barrater)

Each GK IIIb apparatus possesses 3 valves, hence, two sets together using 6 valves. Whereas a KWE-a receiver using 11 valves (all utilising RV 2P800s). In other words, lacking in case of 11 - 6 are 5 valves; 5 x 0.2 A making 1 A.

Its voltage rise - proves to be sufficient enough to employ the voltage drop necessary to allow a regulator device to operate appropriate.

As to avoid problems - when one of the GK IIIb apparatus being switched-off during demonstration; 

as, for instance, showing the difference between: none - single scrambling - and 'double scrambling' which latter should result in descrambling.

Without provisions: demonstrations might causing dangerous voltage swings for the filaments!


But, a LM xxx voltage regulator solves the problem; as it can cope with  > 1 A current. The voltage across it is ca. 6 8 V (the latter voltage might occur when only 3 valves being operated, causing actually, 0.6 A filament current load, instead of 1.2 A.

In a test configuration - the operational (surface) temperature was ca. 28-30° C when operating at ca 1.2 A load, for a considerable time. Only it proved, that the substrate-mounting should be kept insulated from ground. Consequently, this measure will cause some temperature rise. But I suppose, this will increase temperature less than 10° C. 

Though, this has to be tested after modification, soundly.

The regulated 90 V dc output of the NA 6 is employed without external processing.



Most successful proved to be the application of a 1965 - 1980s telephone apparatus (T65)

As have been demonstrated already on YouTube.

Film 00042

Please, be always aware: that the (Siemens)  GK IIIb type "scrambler" transmits only the spectrum: between ca 400 Hz up to maximally ca 1820 Hz; therefore the reproduction of speech is more like that of an old acoustic "gramophone".

That is, as it was then commenced.

The wartime carrier-telephony TF - b (11 kHz carrier) limits at 2000 Hz; hence not too much spectrum difference. (Though, the ratio speech spectrum is: 400 - 1820 Hz versus ca 2100 Hz modulator-switching frequency; against 400 - 2000 Hz versus 11 kHz switching frequency)

Generally speaking:  designing filters at low frequencies is more delicate than at, for instance, 11 kHz. One necessitate far more "iron cores" for filters as well as transformers. Therefore our GK IIIb apparatus are so incredible heavy weighting!

As "ferrox-cubes" were not yet on the market, albeit that Philips Eindhoven was directly, after the war had ended, brought the first samples on the market.

They kept its existence secret for the Germans.

Albeit, that the Germans asked Philips: whether they could produce "magnetic ceramics"?

However, what counts in the case of a link of passing through two GK IIIb scramblers, the application of genuine German field telephones, caused the speech-reproduction passing through two GK IIIb systems being hardly understandable.


In contrast using a  Dutch PTT T65 possesses a far superior frequency response (the real breakthrough was due to improved carbon-microphone design), and due to this the single way reproduction being demonstrated; by means: of on the other end using a German "Lautsprechgerät" (Lsg); by the way its integrated amplifier, driven by a vibrator unit. (12 V).

This allows listening onto the reproduced (scrambled - descrambled) sound by more than a single person; without being hampered by the voice of a T65 operator, too nearby.

The small mains-adapter (near to the mains outlet) is being used for supplying the 48 V line current/voltage.  The Germans designated it: ZB mode (Zentralbatterie). Albeit, that I was once informed that during wartime days this meant 25 V. But Siemens operated regular telephone systems at 60 V.


In the far background, we notice the second GK IIIb scrambler apparatus.



Status:   25 October 2019



Like we arranged during Secret Communications 2, we have created a spot where visitors can view or read book passages

The upper row is not to be touched, without strict permission; whereas the low row can be accessed freely, albeit, with care.



During Secret Communications 2 we also noticed that an old fashioned bureau-lamp is additionally attractive



The GK IIIb scrambler system has got new loudspeakers; but because I discovered that not all German Field telephones were brought into the depot; hence, why not trying one out in combination with the new loudspeakers?

But this was adapted after the next two YouTube films had been uploaded.

However, it operated better than had been encountered in conjunction with the German Lautsprechgerät; its descrambling result is reasonable, but I am not convinced in case of operating one on either sides.



YouTube Films:


Film 00043:    We have brought to function our GK IIIb scrambler modules again, now in the new Secret Communications 3 setup. But operating a T65 type telephone set again, and supplying it by means of a genuine wartime NA 6 unit. Hans is speaking, and his voice being made audible by means of a pair of Logitec loudspeakers. Useless devices;  due to it inferior music reproduction; but fitting well into our current display. A downside encountered, is, that when both scramblers being switched off - that an audible humm appears (50 or 100 Hz). I suppose the source being the simple line-current mains adapter.   



Film 00044:    Explained is our current power supply system. Relying upon a NA 6 unit. My aim being: changing nothing inside, so that it instantly can be operated in conjunction with a KWE-a or LWE-a receiver again. What is made use of, is, the voltage rise due to the less numbers of filaments than in case of a KWE-a:  6 valves maximally (2 x GK IIIb) versus 11 valves in case of operating a KWE-a. The filament supply generated, instead of, say, 2.1 V now 5-6 V. Just employed as to let a LM xx doing its proper voltage regulation (2.1 V).


To be, Deo volente, to be continued, in due course


By Arthur O. Bauer