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.
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 .
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
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.
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
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
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].
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
The Operating Instructions
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
In this YouTube video, Fran Blanche give a full account of the P-55 and its interior .
- A.Q. Tool, Evaluation of the Minifon as a countermeasures data recorder
NRL, memorandum 182, 1 June 1953.
- CIA, Inspection Report - Modified Minifon
26 August 1955 (referring to visit at contractor on 22 August 1955).
- CIA, Modification of Minifons and related antennas
26 August 1955.
- CIA, Modification of Minifons and related antennas (delays)
17 October 1955.
- CIA, Crystal Video Receivers
About the use of Minifon recorders with Crystal Video Receivers.
1 December 1955.
- CIA, Signal Actuate System for Minifon P-55
ELINT, OC-SP/EA. 4 June 1956. SECRET.
- CIA, Request to transfer Five Minifon Trapsports
ELINT, OC_SP. 28 August 1956.
- CIA, Battery and Relay Box for Demand Record System
ELINT, OC-SP. 18 September 1956.
- CIA, Fixed Frequency Oscillator
ELINT, OC-SP/EA. 11 October 1956.
- CIA, Reference Oscillator
Memorandum OC-E. 11 October 1956.
- CIA, New Equipment Designation
Memorandum, 30 October 1956.
- CIA, Development of Audio-Surveillance Equipment at Hohenschoenhausen
21 December 1956.
- 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.
- CIA, Video amplifier for P-55
- CIA, Project RD-128, Quick Reaction Facility
Video recording equipment. See point d, Work Order 4.
5 April 1957.
- CIA, Contract RD-128, Task Order 1, QRF with ...
23 April 1957.
- Allan W. Dulles to Thomas C. Hemmings, Purchase of Minifon by the CIA
12 March 1960.
Roland Schellin, Spion in der Tasche
Detailed history of Protona and the Minifon recorders
ISBN: 3-936012-00-8 (German)
➤ Replaced by 
- Militär Historisches Museum, Achtung Spione (Katalog)
ISBN 978-3-95498-209-7. Dresden, March 2016. p. 348.
- Fran Blanche, World's Smallest All-Tube Spy Recorder - The Minifon P-55
YouTube, 12 April 2019.
- Roland Schellin, Spion in der Tasche (2022)
Completely revised edition, 1 April 2022.
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© Crypto Museum. Created: Saturday 24 March 2012. Last changed: Monday, 28 March 2022 - 11:02 CET.