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- Manufacturer : WM. J. Murdock Co.
- Type : high impedance head set # 56 -1000
- Produced : 1920 - Chelsea, Mass., U. S.
A.
- patented : 1914
- Device : headphones 2x 1000 ohms with
metal diaphragmas
- Operating estimation (1-10) : does work!
- Global estimation (1-10) : 9
- Designed
: backelite, ...
- Specials
: rare type No. 56 - 1000 were used in a
very
early telegraph or telephone
devices and
prebroadcasting RF receivers.
- sample was
used very often from 1914 up to 1925.
- Note : rare and wanted communication part
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