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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 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

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

  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: Friday, 02 December 2016 - 08:36 CET.
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