Interesting applications for vacuum tubes?

[Meterman]

As long as vacuum tubes have been mentioned in this sub-forum, I thought I'd post a picture of one of the items from my collection - a Fisher-Pierce streetlight controller, circa 1960.

It uses two commonly used radio tubes (6SQ7 and 6SK7 I believe), along with a 1P39 phototube.

This would be on a socket mounted a ways up an utility pole and aimed to face north, and once the light on the blue end of the spectrum drops below a set (adjustable) point, the relay trips and energizes whatever may be connected - streetlights, signs, whatnot.
These gave way pretty quickly to the modern plug-type sensors seen on top of streetlights today.

[Vegeta]

Very nice!