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Minifon
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Protona Minifon P-55 L/S
Miniature wire recorder

The Minifon P 55 was a minature wire recorder for audio signals (voice), developed and built in 1955 by Protona GmbH in Hamburg (Germany), as the successor to the Minifon Mi-51. Like the Mi-51, it was built with miniature valves (tubes) and recorded its sound on a very thin metal wire.

The image on the right shows the controls of the P-55, which is housed in a metal enclosure. The machine is completely different from the Mi-51, but it includes a lot of experience and feedback gained from the Mi-51. In other words: without the Mi-51, the P-55 could not have existed.

All controls and connections are at the front of the device. There are four large control push-buttons at the centre and a volume adjustment at the left. At the bottom left is a 3-pin socket for connection of the power suply unit (PSU). At the bottom right is the input/output socket.
  
Close-up of the controls

The P-55 came five years after the first Minifon Mi-51, at a time when the company was going through some bad weather and customers didn't expect much anymore. The P-55 was presented to a small selected audience, just a day before the Hannover Messe (Hannover Fair) of 1955. It was received well and became Protona's mainstream product for the next five years [1]. It wasn't cheap however: at the introduction, the standard model (S) costed DM 925 and the long-play version (L) DM 985 [C]. In the early 1960s, the P-55 was replaced by the Attaché and the Special.

One of the most notorious users of the P-55 was Reinhard Gehlen, head of the post-war German intelligence service OG. During WWII, Wehrmacht major Gehlen had been head of the German military intelligence in the Eastern section. After the war, the Americans had put him in charge of a new German intelligence service that carried his name: Organisation Gehlen (OG). In 1955, the OG ordered more than 80 P-55 units, that were used for covert recording of conversations, even by Reinhard Gehlen himself. In 1956, the OG was renamed to Bundesnachrichtendienst (BND) [2].

The P-55 was also used by the US Central Intelligence Agency (CIA), for various covert (electronic) intelligence gathering applications (ELINT), including automatic recording via a so-called demand receiver [b][c][d]. The units were even modified and re-cased for recording of video signals [k]. According to a CIA report of 21 December 1956, the P-55 was bought in large quantities by the former DDR (East Germany), and modified in a Stasi prison for use by the Russian KGB [h].

The store case of the P55. Unfortunately the top 'leather' part of the flap is missing.
Close-up of the P-55 stored inside the transit case
P-55
The P-55 with the lid open
Close-up of the controls
Close-up of the microphone input connector and some controls
Close-up of the wire spools and the recording head
Close-up of the recording head
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The store case of the P55. Unfortunately the top 'leather' part of the flap is missing.
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Close-up of the P-55 stored inside the transit case
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P-55
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The P-55 with the lid open
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Close-up of the controls
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Close-up of the microphone input connector and some controls
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Close-up of the wire spools and the recording head
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Close-up of the recording head

Accessories
Over 20 different accessories were available for the P-55, ranging from a variety of microphones, to the storage case. The price for the latter (empty) was DM 75 in June 1958 [4] . The Operating Instructions [2] list the following add-ons:

  • Crystal microphone (standard)
  • Table speaker/microphone
  • Wrist-watch microphone
  • Throat microphone
  • Dynamic (moving coil) microphone
  • Stetoset phones
  • Single type ear-set
  • Electrical foot control
  • Mechanical foot control
  • Telephone pick-up
  • Recording & play-back cable
  • Car battery adapter
  • Telephone transformer
  
Close-up of the P-55 stored inside the transit case

The 'standard' microphone supplied with the Mi-51. Attaches to clothing with a leather strap.
The headphones in the shape of a stethoscope
The famous microphone that was disguised as a typical watch
Play cable for connecting the P-55 to an external amplifier
A spare wire spool in a storage box
Some accessories
Mains adapter (PSU)
Car battery adapter
This holster allowed the Minifon to be carried under the clothing
Chrhstal microphone
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The 'standard' microphone supplied with the Mi-51. Attaches to clothing with a leather strap.
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The headphones in the shape of a stethoscope
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The famous microphone that was disguised as a typical watch
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Play cable for connecting the P-55 to an external amplifier
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A spare wire spool in a storage box
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Some accessories
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Mains adapter (PSU)
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Car battery adapter
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This holster allowed the Minifon to be carried under the clothing
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Chrhstal microphone

Video
In this YouTube video, Fran Blanche give a full account of the P-55 and its interior [3].




Literature
  1. A.Q. Tool, Evaluation of the Minifon as a countermeasures data recorder
    NRL, memorandum 182, 1 June 1953.

  2. CIA, Inspection Report - Modified Minifon
    26 August 1955 (referring to visit at contractor on 22 August 1955).

  3. CIA, Modification of Minifons and related antennas
    26 August 1955.

  4. CIA, Modification of Minifons and related antennas (delays)
    17 October 1955.

  5. CIA, Crystal Video Receivers
    About the use of Minifon recorders with Crystal Video Receivers.
    1 December 1955.

  6. CIA, Signal Actuate System for Minifon P-55
    ELINT, OC-SP/EA. 4 June 1956. SECRET.

  7. CIA, Request to transfer Five Minifon Trapsports
    ELINT, OC_SP. 28 August 1956.

  8. CIA, Battery and Relay Box for Demand Record System
    ELINT, OC-SP. 18 September 1956.

  9. CIA, Fixed Frequency Oscillator
    ELINT, OC-SP/EA. 11 October 1956.

  10. CIA, Reference Oscillator
    Memorandum OC-E. 11 October 1956.

  11. CIA, New Equipment Designation
    Memorandum, 30 October 1956.

  12. CIA, Development of Audio-Surveillance Equipment at Hohenschoenhausen
    21 December 1956.

  13. CIA, A limited analysis and appraisal of the Minifon Recorder Model P-55 L
    Report No. 151-B. 9 December 1957. Partly declassified by CIA on 6 December 2012.

  14. CIA, Video amplifier for P-55
    Date unknown.

  15. CIA, Project RD-128, Quick Reaction Facility
    Video recording equipment. See point d, Work Order 4. 5 April 1957.

  16. CIA, Contract RD-128, Task Order 1, QRF with ...
    23 April 1957.

  17. Allan W. Dulles to Thomas C. Hemmings, Purchase of Minifon by the CIA
    12 March 1960.
Documentation
  1. Operating Instructions for Your Minifon P-55
    Official instruction manual (24 pages + 2 pages supplement) (English).
    Protona GmbH, November 1957.

  2. Das Neue Minifon P55
    Sales brochure (German).
    Protona GmbH, March 1957.

  3. Preisliste für minifon P 55 - und Spezialzubehör
    Price list for the Minifon P-55 and special accessories (German).
    Protona GmbH, 1958.

  4. Minifon modified circuit diagram
    CIA, undated.
References
  1. Roland Schellin, Spion in der Tasche
    Detailed history of Protona and the Minifon recorders
    ISBN: 3-936012-00-8 (German)  Replaced by [4]

  2. Militär Historisches Museum, Achtung Spione (Katalog)
    ISBN 978-3-95498-209-7. Dresden, March 2016. p. 348.

  3. Fran Blanche, World's Smallest All-Tube Spy Recorder - The Minifon P-55
    YouTube, 12 April 2019.

  4. Roland Schellin, Spion in der Tasche (2022)
    Completely revised edition, 1 April 2022.
    ISBN 978-3982234007.  Amazon
Further information
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© Crypto Museum. Created: Saturday 24 March 2012. Last changed: Monday, 28 March 2022 - 11:02 CET.
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