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← Minifon
  
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 by Protona GmbH in Hamburg (Germany). It was introduced in 1955 as the successor to the Mi-51. Like the Mi-51, it was built with miniature valves (tubes) and recorded sound on a very thin 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 machine. 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 would be 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 [4]. In the early 1960s, the P-55 was replaced by the Attaché and the Special.

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

References
  1. Roland Schellin, Spion in der Tasche
    Detailed history of Protona and the Minifon recorders
    ISBN: 3-936012-00-8 (German)

  2. Protona GmbH, Operating Instructions for Your Minifon P-55
    Official instruction manual (24 pages + 2 pages supplement), December 1957 (English)

  3. Protona GmbH, Das Neue Minifon P55
    Sales brochure, March 1957

  4. Protona GmbH, Preisliste für minifon P 55 - und Spezialzubehör
    Price list for the Minifon P-55 and special accessories, 1958 (German)
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Crypto Museum. Created: Saturday 24 March 2012. Last changed: Tuesday, 13 June 2017 - 17:59 CET.
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