[flavio81]

Really cool pictures!

Light bulbs are sometimes used for stabilizing oscillators. I think it works like an (audio) volume "compressor" would.

For example the Thorens TD125 turntable uses a light bulb as part of the oscillator circuit that generates the AC signal that powers the motor.

[notlob]

A bulb was also a neat hack used in the 200A, the first product made by a small and relatively obscure garage startup in Palo Alto: https://en.m.wikipedia.org/wiki/HP200A