An EM84 " magic eye " tuning indicator valve was used.
2.
Early models had a magic eye tube tuning indicator in front.
3.
Tuning indicator tubes were used in vacuum tube receivers from around 1936 to 1980 before vacuum tubes were replaced by transistors in radios.
4.
The magic eye tube was the first in a line of development of cathode ray type tuning indicators developed as a cheaper alternative to the needle movement meters.
5.
The unit may be changed to a different frequency in the field by replacing the crystal and adjusting tuned circuits, using tuning indicator ID-292 / PRC-6.
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