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Detective Dictograph



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First transistors USSR


My works

Tube stereo cassette player

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RussianAudio recorders Televisions, video Tube radios NEW Other rarities My works


Minifon Mi51




Used Google translator

     Minifon Mi51 (Mi 51).  Portable lamp wire recorders. Made from 1951 to 1955. From 1951 to 1953, their company produced "Monske & Co. GmbH", Hannover, and from 1953 to 1955 - the company "Protona GmbH"; Hamburg, Germany. In 1955 began the production of the following model Minifon P55. I have a recorder, two Mi51, externally applied in these different types of batteries. In fact, the differences are much greater. If you remove the spool and carefully consider the deck, you will see that there are structural differences. If you look at the kinematics of the inside, it is immediately obvious that, while maintaining the overall layout, they differ not only structurally, but also the quality of manufacture, the materials used. In the left column there are photos of the recorder manufactured by "Protona GmbH" and in the right one by "Monske & Co. GmbH". The device manufactured by "Protona GmbH" inside looks much better. Nevertheless, the mechanics of both machines was fully working, break down there is just nothing. To transfer motion from the engine used "eternal" belt a coiled spring, and there is no detail, which would have used rubber.

Video review

In the left column there are photos of the recorder manufactured by "Protona GmbH" (1953 - 1955), and in the right one by "Monske & Co. GmbH" (1951 - 1953).

Photos can be enlarged


In the photo on the right, there is an inscription on the cover latch "Monske & Co"


     Dimensions recorder 170 x 110 x 37 mm, weight 750 g without batteries. Since recorders lamp, for their nutrition requires three different voltages. Filament voltage 1,5 v - AA batteries, the power of the anode 30 v - battery type 413, and the power of the engine - a special battery 12 v, or two to 9 v, connected in parallel (of the company "Monske & Co. GmbH"). Engine speed of both recorders is stable in the range of power supply 8 - 12 v, and today can be used to replace the battery 9 v, type PP3. To supply the anode, I made the right size pack of three batteries MN, 12 v + 12 v + 6 v = 30 v. The electrical circuit collected on three subminiature vacuum tube type DF67 (2 pieces), and DL67 (1 item). Electronics board both devices do not differ structurally.


Electrical circuit Minifon Mi51 (Mi 51). Photo from the book by Roland Shellin "Minifon The Spy in Your Pocket", (Roland Schellin, "Minifon Der spion in der tasche")


Below is a photo of the electronics board of the device of the company "Protona GmbH".


In the photo from left to DF67 lamp, and on the right DL67. Actual sizes DF67 - 26 x 7.8 mm, DL67 - 34,5 x 7,5 mm.


Universal magnetic head, and a magnet replaces the erase head



The stamp on the underside of the deck of the apparatus of the company "Protona GmbH"

     To reduce the impact of volatility of the wire, take-up spool has a noticeably larger diameter, and head while working smoothly moves up - down, putting the wire in neat rows. According to this principle at that time was done, most stationary wire recorders. Minifon also was the first truly portable recorder. Naturally, he was very popular, not only from honest citizens, but also to detectives and intelligence services around the world. In Germany it is sold for a price of 730 DM. Our secret police may also use them as such domestic recorders did not exist.

In the late 50's, or early 60-ies in the USSR began to produce an analog - a wire recorder "Собеседник" (Interlocutor) for the KGB. Photograph of such a device has sent me a famous collector of espionage equipment Detlev Vreisleben (Germany). This recorder is in the in the Museum of the Czech Police in Prague.

Wire Recorder "Собеседник" (Interlocutor)
Unfortunately, there is no such recorder in my collection, and the only known copy is in the Museum of the Czech Police in Prague.


On the upper photo of the "Sobesednik" that Detlev Vreisleben sent me, this is an old exposition. Below is a photograph of the "Sobesednik", which I personally made in 2017 in the Museum of the Czech Police in Prague, this is a new exposition, the recorder is placed vertically.


       If you compare the designs of "Sobesednik" and "Minifon Mi51", it is clear that they have a similar mechanics, but the electronics are completely different. Amplifier "Sobesednik" is assembled on 4 transistors Raytheon, two of which are visible marking CK721. Condensers are also foreign-made, and the resistors are similar to Soviet-type MLT, but without labeling. Of the foreign components in the USSR, they made special equipment intended for use in "Western" countries for the depersonalization of the producer's country. In any case, it is written in the article about special equipment in the magazine "Men's work" No. 49.
This photo was shared with me by Roland Schellin, a well-known technology historian and writer from Germany.

     Use wire in Minifon Mi51 as a magnetic carrier allowed to reach a very large recording. At the coil diameter of 44 mm wire is placed for 4 hours of work at a speed of 23 cm / sec. The wire is very thin, diameter 0,05 mm, but tough enough, and by itself is not broken. Truncations occur only when it is detached from the reel and is wound on the shaft beneath it. Truncations are eliminated by a simple binding knot the ends. To prevent soskakivaniya wire on the head there is a flat spring, and under the coils, a well-designed brake system. All this really works well, and problems with the cliffs, as a rule does not arise. Office carried out two handles - buttons that need pushing or pulling.

The photo on the left of the stop mode, the right photo mode "record - play."


When the recording or playback, the lateral extension includes a mode button rewind.


     To switch between recording modes - play a special switch is not. If the plug is inserted into the recorder microphone, recording mode. Play mode is activated if the recorder is inserted into the plug headphones. The length of the microphone plug 15 mm and a length of 25 mm headphone plug. Longer plug headphones clicks on the pushers, switching contact group on-board electronics in the playback mode. Erasing a record is in rewind mode, using a permanent magnet located near the head. The holder of a magnet fixed on the axis, and fed - is given manually. It has a pin, which stands out through the arcuate slot in the lid body. The connectors for connecting the power supply are found in the devices in different places (photo below). Round lock housing cover is on top, next to the battery compartment.


The photo on the left of the original battery 12 v power of the engine and the original packing box. The photo on the right original battery type 30 v Mallory RM-413, a modern analogue Eveready 413, and a homemade battery 30 v, collected from three batteries MN (12 v + 12 v + 6 v).


A set of original batteries for recorders Minifon Mi51


In the photo below a homemade battery power engine 9 v.


Self-made batteries 12 v and 30 v.


Produced with different number of coils of wire, at 1 - 4 hours recording. One of the coils came with the recorder, was new and sealed. On the seal there is a reprint "Protona".  


A set of accessories for the device of the company "Protona GmbH". In the set were, power supply, microphone, headphones - stethoscope, a device for recording telephone conversations, 5 rolls of wire, and instruction manual.


In the photo below, a spoiled mercury battery of 1.4 V - "Mercury Energizer" in the recorder of the company "Protona GmbH" is visible. It was unusual. The shape and dimensions are the same as in modern AA batteries, but the polarity is reversed. Also in the apparatus was perfectly preserved anode battery Mallory, 29 v, type RM-413.


     Both devices were sealed, that is, to me they no who did not climb up. A piece of wire, mounted inside the body, passed through a hole in the deck, went out into the cup for filling, and pressed into her lead seals. Thus, without violating the seal, remove the deck from the hull can not. On the stamps have stamp "Minifon" and the figure.


On the inside of the cover of the device "Protona GmbH" there is a sticker with warranty information. Covers also differ in the way they are fastened. In the recorder "Monske & Co. GmbH" instead of the rotary latch, a screw is used.


Recorder company "Monske & Co. GmbH" was with a cover, but without accessories. For recorders in this series were issued special spy accessories, such as a microphone, under the camouflage watches, a device for recording telephone conversations, a miniature microphone with a clip, and other accessories.



Specification Minifon Mi51 (Mi 51). Photo from the book by Roland Shellin "Minifon The Spy in Your Pocket", (Roland Schellin, "Minifon Der spion in der tasche").



Operating instructions for Minifon Mi51 (Mi 51) from "Protona GmbH".


In fact, the documentation for these recorders does not mention Mi51, it was simply called Minifon. However, the binding to the model year was still used, for example, the name Minifon 53 is used in advertising.