"A Tuning eye (tube or valve), is a tube that gives a visual indication for audio output, signal strength or other functions. It is also called cat's eye, or tuning eye tube. They were fitted on radio receivers from around 1936 onwards, replacing the earlier "Tuneon" neon lamp type tuning indicators, as a novel selling feature." (Source Wikipedia.org)
I managed to acquire a Tesla EM-11 Tube these days. It's used, but in great shape. I plan to build a simple circuit to see it working. Here are some pictures:
More details on this tube are available on RadioMuseum.
The schematics for the circuit I plan to build are as follows:
The components values are:
R8 adjustable 100k
D1 30V Z-Diode
When this is done, I will post a film as well.