Wire recording

A Drahttongerät used for storing of sound waves. The Danish physicist Valdemar Poulsen invented around 1890, a device for storing notes on a steel wire, and thus the first Drahttongerät. The device he called telegraphone.

A steel wire is fed past an electromagnet. The electromagnet is connected to a microphone, which converts the sound waves into an AC voltage, and the steel wire by means of magnetic induction, leaving a residual magnetization. If one then passes the magnetized steel wire back to the solenoid, in which an electrical voltage is induced, which makes audible the original signal in a speaker connected to the electromagnet.

Drahttongeräte were quite prevalent in the United States in the 1940s and 1950s, in Germany they reached only minor importance. In the 1950s, they were replaced by tape recorders. Only in flight recorders they lasted a little longer.

Wires made of chromium-manganese steel (15% Cr, 12% Mn) were used as wire material in the 30s mostly. The diameter was 0.11 mm and 0.22 mm for music for voice recordings. Later, the manganese was replaced by nickel (18% Cr, 8% Ni), as a strength wires of 0.09 mm diameter were used.