Minifon Armband-Mikrofon - Wrist watch microphone ohne Schalter

Protona Armband-Mikrofon zur Verwendung z.B. mit dem Minifon P55. Das Kristallmikrofon ist in ein Armbanduhr-Gehäuse eines Chronographen eingebaut, die Uhr selbst ist Attrappe und hat keine Funktion.

Ausführung ohne Schalter (Fernsteuerung des Minifons). Siehe auch Armbandmikrofon mit zusätzlicher Schaltfunktion.

Wristwatch microphone.
Microphone embedded in fake watch
Microphone with crystal transducer
There is no watch mechanism, the hands do not move.
Buttons not operational in the normal model.
There is a version in which the buttons act as a remote control for the M51 or M55 recorder.
Microphone output on internally connected and non-removable cable.
1 meter long cable to end in a 3.5 mm audio plug.
Typical DC impedance:  measured from 4 MΩ to 5 MΩ.
Maximum output signal of about 500 mV of amplitude when submitted to a loud voice.
Leather bracelet.

Application
Used in espionage operations as an input to the spy recorders manufactured by Minifon and Protona in the period from 1950 to 1965.
The cable was hidden under the sleeve of the shirt and carried the signal to the pocket recorder.

In questo link sono elencati 34 modelli, di cui 29 con immagini e 12 con schemi.
Elenco delle radio e altri apparecchi della Protona, R. Stach; Hamburg, Hannover (siehe auch Monske)