| 6977 / DM160 (Unknown Mfr.) |
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| Written by AnubisTTP on 2007-10-06 |
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At a mere 25mm in length, the 6977 is considered by most tube collectors to be the world's smallest eye tube. This is not strictly accurate: the 6977 has a control grid, but the indicator has no shadow or other measure of an analog value. The control grid simply varies the brightness of the glow, not the glow area. That being said, the 6977 is a unique device, a subminiature triode with a phosphor coating that visually indicates the tube's internal state. The 6977 was originally designed as a logic indicator for early computer systems, but saw nearly as much use as a triode for battery powered radios and similar devices.
The 6977 "eye tube" operates at 30 volts.
6977 indicator with US quarter for scale.
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