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- Manufacturer : Nathaniel Baldwin
- Produced : 1915 - Salt Lake
City, Utah, U. S. A.
- patented : May 10, 1910;
Sept. 14, 1915
- Device : sensitive high impedance (1200
ohms) pending system headphones
- Operating estimation (1-10) : 10
- Global estimation (1-10) : 10
- Designed
: backelite, ...
- Specials : mica diaphragmas with
pending system cores
- Note : one
of the first model of head set used by spark or early crystal radio
receivers
- it was used in military communication devices
in WW1 too.
- very early and wanted!
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